Information processing device and information processing method

ABSTRACT

Generation and management of a communication path between a plurality of information processing devices are properly performed. 
     An information processing device is an information processing device equipped with a communication unit and a control unit. The communication unit performs exchange of a signal for generation or updating of a multi-hop communication path using wireless communication with another information processing device. In addition, the control unit performs control to change a metric value included in the signal for generation or updating of the multi-hop communication path based on a state of the information processing device.

TECHNICAL FIELD

The present technology relates to an information processing device.Particularly, the technology relates to an information processing deviceand an information processing method for dealing with informationregarding wireless communication.

BACKGROUND ART

In the related art, there are wireless communication technologies forexchanging various kinds of data using wireless communication. Forexample, a communication method for making an autonomous connection witha nearby information processing device (for example, ad hoccommunication or an ad hoc network) has been proposed (for example, seePatent Literature 1).

CITATION LIST Non-Patent Literature

Patent Literature 1: JP 2009-239385A

SUMMARY OF INVENTION Technical Problem

According to the technology of the related art mentioned above, variouskinds of data can be exchanged between two information processingdevices using wireless communication, without connection on a wirednetwork. In addition, on such a network, each information processingdevice can perform communication with a nearby information processingdevice, without depending on a master station such as a control device.Furthermore, on an ad hoc network, when a new information processingdevice appears nearby, this new information processing device can alsofreely participate in the network. Thus, network coverage can be widenedin accordance with an increase of nearby information processing devices.

In addition, on top of such an autonomous connection with a nearbyinformation processing device, each information processing device canalso transfer information to be exchanged with another informationprocessing device in a bucket brigade manner (which is so-calledmulti-hop relay). In addition, a network using multi-hop is generallyknown as a mesh network.

As described above, on an ad hoc network or a mesh network, it ispossible to freely communicate with nearby information processingdevices. In addition, the network can be expanded while connections withinformation processing devices around are being made. In this case, itis important to appropriately generate and manage a communication pathbetween the plurality of information processing devices.

The present technology takes the above circumstances into consideration,and aims to properly generate and manage a communication path between aplurality of information processing devices.

Solution to Problem

The present technology has been made in order to solve theabove-mentioned issues. According to a first aspect of the presenttechnology, there is provided an information processing device, aninformation processing method, and a program causing a computer toexecute the method, the information processing device including: acommunication unit configured to perform exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and a controlunit configured to perform control to change a metric value included inthe signal based on a state of the information processing device.Accordingly, an effect of changing a metric value based on a state of aninformation processing device is exhibited.

According to the first aspect, when the information processing device ismoving, the control unit may set the metric value to be large.Accordingly, an effect of setting a metric value to be large when theinformation processing device is moving is exhibited.

According to the first aspect, when an amount of traffic of theinformation processing device is larger than a threshold value, thecontrol unit may set the metric value to be large. Accordingly, aneffect of setting a metric value to be large when an amount of trafficof the information processing device is larger than the threshold valueis exhibited.

According to the first aspect, when an error rate of each link is lowerthan a threshold value, the control unit may compute the metric valueusing the error rate, and when the error rate is higher than thethreshold value, the control unit may compute the metric value withoutusing the error rate. Accordingly, an effect that, when an error rate ofeach link is lower than the threshold value, a metric value is computedusing the error rate and when the error rate is higher than thethreshold value, the metric value is computed without using the errorrate is exhibited.

According to the first aspect, when a time elapsed from a final datatransmission time to an information processing device which isdesignated as a next transmission destination on the communication pathis longer than a threshold value, or when a difference between anelectric field intensity at the time of the final data transmission tothe information processing device and a current electric field intensityis larger than a threshold value, the control unit may estimate themetric value based on the current electric field intensity. Accordingly,an effect that, when a time elapsed from the final data transmissiontime to the information processing device which is designated as a nexttransmission destination is longer than the threshold value or when thedifference between the electric field intensity at the time of the finaldata transmission to the information processing device and a currentelectric field intensity is larger than the threshold value, a metricvalue is estimated based on the current electric field intensity isexhibited.

According to the first aspect, when data transmission to the informationprocessing device which is designated as the next transmissiondestination on the communication path is performed, the control unit maycompute the metric value using a value obtained by averaging a rate ofthe data using a low-pass filter, and when the metric value is estimatedbased on the current electric field intensity and a rate of the data atwhich transmission has succeeded has been acquired, the control unit maycompute the metric value using the rate of the data as an initial valueof the low-pass filter. Accordingly, an effect that, when datatransmission to the information processing device which is designated asthe next transmission destination is performed, a metric value iscomputed using the value obtained by averaging the rate of the datausing the low-pass filter, and when the metric value is estimated basedon the current electric field intensity and a rate of the data at whichtransmission has succeeded has been acquired, the metric value iscomputed using the rate of the data as the initial value of the low-passfilter is exhibited.

According to the first aspect, when the rate of the data is used as theinitial value of the low-pass filter, the control unit may use a metricvalue estimated based on the current electric field intensity after thesetting of the initial value, then use an average value of the estimatedmetric value and an output value of the low-pass filter, and then usethe output value of the low-pass filter. Accordingly, an effect that,when the rate of the data is used as the initial value of the low-passfilter, the metric value estimated based on the current electric fieldintensity is used after the setting of the initial value, then theaverage value of the estimated metric value and an output value of thelow-pass filter is used, and then the output value of the low-passfilter is used is exhibited.

According to the first aspect, when link broken is set if an error rateof each link is higher than a threshold value, the control unit maylower the error rate each time a predetermined period of time elapsesfrom the link broken. Accordingly, an effect that, when link broken isset if an error rate of each link is higher than the threshold value,the error rate is lowered each time the predetermined period of timeelapses from link broken is exhibited.

According to the first aspect, when there is a communication path setbased on a magnitude of the metric value, and there is anothercommunication path having a metric value which is a metric value smallerthan the metric value relating to the communication path and whosedifference with the metric value relating to the communication path ishigher than a metric threshold value, the control unit may set the othercommunication path as a new communication path. Accordingly, an effectthat, when there is the communication path set based on the magnitude ofa metric value, and there is another communication path having a metricvalue which is a metric value smaller than the metric value relating tothe communication path and whose difference with the metric valuerelating to the communication path is higher than the metric thresholdvalue, the other communication path is set as a new communication pathis exhibited.

According to the first aspect, when there are a plurality of othercommunication paths, the control unit may set a communication pathhaving a smallest metric value among the plurality of communicationpaths as the new communication path. Accordingly, an effect that, whenthere are a plurality of other communication paths, a communication pathhaving the smallest metric value among the plurality of communicationpaths is set as a new communication path is exhibited.

According to the first aspect, when there is the communication path setbased on the magnitude of the metric value, and there is anothercommunication path having a metric value which is a metric value smallerthan the metric value relating to the communication path and whosedifference with the metric value relating to the communication path isnot higher than a metric threshold value, the control unit may set theother communication path as the new communication path on a conditionthat this state continues for a predetermined period of time or apredetermined number of times. Accordingly, an effect that, when thereis a communication path set based on the magnitude of a metric value andthere is another communication path having a metric value which is ametric value smaller than the metric value relating to the communicationpath and whose difference with the metric value relating to thecommunication path is higher than the metric threshold value, the othercommunication path is set as a new communication path on the conditionthat the state continues for the predetermined period of time or thepredetermined number of times is exhibited.

According to the first aspect, when the information processing device ismoving, the control unit may set the metric threshold value to be small.Accordingly, an effect that, when the information processing device ismoving, the metric threshold value is set to be small is exhibited.

According to the first aspect, when the information processing device ismoving, the control unit may set a value relating to the predeterminedperiod of time or the predetermined number of times to be small.Accordingly, an effect that, when the information processing device ismoving, the value relating to the predetermined period of time or thepredetermined number of times is set to be small is exhibited.

According to the first aspect, when priority of communication performedusing the communication path is high, the control unit may set themetric threshold value to be large, and when the priority is low, thecontrol unit may set the metric threshold value to be small.Accordingly, an effect that, when priority of communication performedusing a communication path is high, the metric threshold value is set tobe large, and when the priority is low, the metric threshold value isset to be small is exhibited.

According to the first aspect, when priority of communication performedusing the communication path is high, the control unit may set a valuerelating to the predetermined period of time or the predetermined numberof times to be large, and when the priority is low, the control unit mayset the value relating to the predetermined period of time or thepredetermined number of times to be small. Accordingly, an effect that,when priority of communication performed using a communication path ishigh, the value relating to the predetermined period of time or thepredetermined number of times is set to be large, and when the priorityis low, the value relating to the predetermined period of time or thepredetermined number of times is set to be small is exhibited.

According to the first aspect, when the number of information processingdevices on the communication path is larger than a hop threshold value,the control unit may set the metric threshold value to be small.Accordingly, an effect that, when the number of information processingdevices on a communication path is larger than the threshold value ofhop, the metric threshold value is set to be small is exhibited.

According to the first aspect, when the number of information processingdevices on the communication path is larger than a hop threshold value,the control unit may set a value relating to the predetermined period oftime or the predetermined number of times to be small. Accordingly, aneffect that, when the number of information processing devices on acommunication path is larger than the hop threshold value, the valuerelating to the predetermined period of time or the predetermined numberof times is set to be small is exhibited.

According to the first aspect, when the number of times thecommunication path is changed is larger than a threshold value of thechange, the control unit may set the metric threshold value to be small.Accordingly, an effect that, when the number of times of thecommunication path change is larger than the threshold value of thechange, the metric threshold value is set to be small is exhibited.

According to the first aspect, the control unit may set the valuerelating to the predetermined period of time or the predetermined numberof times to be small when the number of times of the communication pathchange is larger than the threshold value of the change. Accordingly, aneffect that, when the number of times of the communication path changeis larger than the threshold value of the change, the value relating tothe predetermined period of time or the predetermined number of times isset to be small is exhibited.

Advantageous Effects of Invention

According to the present technology, the excellent effect ofappropriately generating and managing communication paths between aplurality of information processing devices can be exhibited. It shouldbe noted that the effect described here is not necessarily limitative,and any effect described in the present disclosure may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a system configuration example of acommunication system 200 according to a first embodiment of the presenttechnology.

FIG. 2 is a block diagram showing an internal configuration example ofan information processing device 100 according to the first embodimentof the present technology.

FIG. 3 is a diagram showing an example of a signal format of a packetexchanged between information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology.

FIG. 4 is a diagram showing examples of signal formats of a managementpacket exchanged between the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 5 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 6 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 7 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 8 is a diagram schematically showing an example of a mesh pathtable (mesh path table 340) retained by each of information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 9 is a diagram showing a generation example of a mesh path retainedby each of the information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology.

FIG. 10 is a diagram showing a generation example of a mesh pathretained by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 11 is a diagram schematically showing another example of the meshpath table (mesh path table 350) retained by each of the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 12 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 13 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 14 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 15 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 16 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 17 is a diagram schematically showing still another example of themesh path table (mesh path table 360) retained by each of theinformation processing devices which constitute the communication system200 according to the first embodiment of the present technology.

FIG. 18 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 19 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 20 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 21 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 22 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 23 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 24 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 25 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to asecond embodiment of the present technology.

FIG. 26 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 27 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 28 is a diagram schematically showing still another example of themesh path table (mesh path table 370) retained by each of theinformation processing devices which constitute the communication system200 according to the second embodiment of the present technology.

FIG. 29 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 30 is diagram schematically showing a computation process of ametric value by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 31 is a diagram schematically showing path selection of thecommunication system 200 according to the second embodiment of thepresent technology.

FIG. 32 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 33 is a diagram schematically showing still another example of themesh path table (mesh path table 380) retained by each of theinformation processing devices which constitute the communication system200 according to the second embodiment of the present technology.

FIG. 34 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 35 is a diagram showing four access categories (ACs) of IEEE802.11e-Enhanced Distributed Channel Access (EDCA).

FIG. 36 is a block diagram showing an example of a schematicconfiguration of a smartphone.

FIG. 37 is a block diagram showing an example of a schematicconfiguration of a car navigation device.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for implementing the present technology (whichwill be referred to hereinafter as embodiments) will be described.Description will be provided in the following order.

1. First embodiment (Example in which an expiration time and updatingexpiration time of a path metric are set)

2. Second embodiment (example in which a path metric value is changed)

3. Application example

1. First Embodiment Configuration Example of a Communication System

FIG. 1 is a diagram showing a system configuration example of acommunication system 200 according to a first embodiment of the presenttechnology.

The communication system 200 includes a plurality of informationprocessing devices (an information processing device 100, an informationprocessing device 210, an information processing device 220, aninformation processing device 230, and an information processing device240). Each of the information processing devices constituting thecommunication system 200 is, for example, a portable type informationprocessing device or a fixed type information processing device with awireless communication function. It should be noted that portable typeinformation processing devices include wireless communication devices,for example, smartphones, mobile telephones, tablet terminals, and fixedtype information processing devices include information processingdevices such as printers, personal computers, and the like.

In FIG. 1 rectangles representing the information processing devices arelabeled with reference symbols (A to E) for identifying the respectiveinformation processing devices. In other words, the rectanglerepresenting the information processing device 100 is labeled “A,” therectangle representing the information processing device 210 is labeled“B,” the rectangle representing the information processing device 220 islabeled “C,” the rectangle representing the information processingdevice 230 is labeled “D,” and the rectangle representing theinformation processing device 240 is labeled “E.” In addition, thereference symbols A to E are used to display the content of signalsexchanged between the information processing devices as shown in FIGS.9, 10, and the like.

In addition, FIG. 1 shows communication paths between the informationprocessing device 100 and the information processing devices 210, 220,and 230 using dotted lines 251, 253, and 254. In addition, communicationpaths between the other information processing devices are likewiseindicated using dotted lines 252 and 255 to 257.

Here, as a communication method for autonomously connecting with anearby information processing device, ad hoc communication, an ad hocnetwork, and the like are known. On such a network, each informationprocessing device can perform communication with a nearby informationprocessing device without depending on a master station (for example, acontrol device). Thus, in this embodiment of the present technology, anad hoc network will be exemplified as a communication method forautonomously connecting with a nearby information processing device

When a new nearby information processing device is added on an ad hocnetwork, this new information processing device can freely participatein the network. For example, a case in which, among the informationprocessing devices shown in FIG. 1, only the information processingdevice 100, the information processing device 210, the informationprocessing device 220 first participate in the ad hoc network isassumed. In this case, the information processing device 230 and theinformation processing device 240 are assumed to be added in order. Inthis case, as the number of the information processing devices (nearbyinformation processing devices) increases, coverage of the network canbe widened. That is, according to the addition of the informationprocessing device 230 and the information processing device 240 inorder, coverage of the network can be widened.

Here, on top of autonomous connection with a nearby informationprocessing device, each information processing device can also transferinformation to be exchanged with another information processing devicein a bucket brigade manner.

It is assumed that, for example, the information processing device 100can directly communicate with each of the information processing devices210, 220, and 230, but is not able to directly communicate with theinformation processing device 240 for a reason such as radio wavesfailing to reach the device.

When direct communication is not possible as described above, theinformation processing devices which can directly communicate with theinformation processing device 100 (the information processing devices210, 220, and 230) can transfer data of the information processingdevice 100 to the information processing device 240. Thus, such transferof data enables the information processing device 100 and theinformation processing device 240 which does not directly communicatewith the information processing device 100 to exchange information viaany of the information processing devices 210, 220, and 230.

This method of performing data transfer between devices (so-calledbucket brigade) as described above to cause information to reach aremote information processing device is called multi-hop relay. Inaddition, a network which performs multi-hop is generally known as amesh network.

A configuration of an information processing device which constitutessuch an ad hoc network or a mesh network is shown in FIG. 2. Inaddition, multi-hop relay will be described in more detail withreference to FIGS. 4, 10, and the like.

In addition, among the information processing devices which constitutethe communication system 200 in the embodiments of the presenttechnology, an information processing device which serves as a reference(for example, an information processing device which receives a signal)will be referred to as a self-station, and other information processingdevices will be referred to as a transmitting station, a receivingstation, a transmission source station, a destination station, and anearby station.

In more detail, an information processing device which transmits asignal received by the self-station will be referred to as atransmitting station, and an information processing device whichreceives a signal from the self-station will be referred to as areceiving station. In addition, a transmission source informationprocessing device which first transmits a signal received by theself-station (a so-called leader of a bucket brigade) will be referredto as a transmission source station, and an information processingdevice which receives a signal received by the self-station in the end(a so-called terminus of the bucket brigade) will be referred to as adestination station. In addition, an information processing device whichtransfers a signal received by the self-station will be referred to as arelay station, and an information processing device which is near or inthe vicinity of the self-station on a network will be referred to as anearby station.

[Configuration Example of an Information Processing Device]

FIG. 2 is a block diagram showing an internal configuration example ofthe information processing device 100 according to the first embodimentof the present technology. Herein, only the information processingdevice 100 will be described because internal configurations of theother information processing devices (the information processing devices210, 220, 230, and 240) are the same as that of the informationprocessing device 100, and thus other information processing deviceswill not be described.

The information processing device 100 includes an antenna 110, acommunication unit 120, an input/output (I/O) interface 130, a controlunit 140, and a memory 150. In addition, these units are connected toone another via a bus 160.

The communication unit 120 is a module (for example, a modem) forperforming transmission and reception of radio waves via the antenna110. For example, the communication unit 120 can perform wirelesscommunication through millimeter wave communication (60 GHz, etc.), awireless local area network (LAN) of 900 MHz, 2.4 GHz, or 5 GHz, or anultra-wide band (UWB). In addition, the communication unit 120 canperform wireless communication through, for example, visible lightcommunication or near field communication (NFC).

For example, the communication unit 120 exchanges a signal (an RANN, aPREQ, or a PREP) for generating or updating a communication path ofmulti-hop using wireless communication with another informationprocessing device based on control of the control unit 140. The RANN,PREQ, and PREP will be described in detail with reference to FIG. 4, andthe like.

It should be noted that the communication unit 120 may be designed toperform wireless communication using radio waves (electromagnetic waves)or wireless communication using a medium other than radio waves (forexample, wireless communication performed using a magnetic field).

In addition, the communication unit 120 performs communication with anearby information processing device by setting up a communication link,manages the number of nearby information processing devices with whichthe information processing device 100 can communicate, and retainsinformation which indicates the number of nearby communicableinformation processing devices (communicable device number information).Furthermore, the communication unit 120 regularly or irregularlyobserves a degree of use of a channel used in wireless communication,and retains information which indicates a level of congestion of acommunication line around the information processing device 100(congestion level information). In addition, the communication unit 120observes link quality (reception power, a transmittable data rate, etc.)with a nearby information processing device performing wirelesscommunication therewith, and retains information which indicates abandwidth which makes wireless communication with a nearby informationprocessing device possible (communication state information). Then, thecommunication unit 120 supplies the information to the control unit 140.

The I/O interface 130 is an interface with an external device such as asensor actuator which operates in linkage with the informationprocessing device 100. FIG. 2 shows an example in which, for example, amovement detection unit 171, an operation reception unit 172, a displayunit 173, and an audio output unit 174 are connected with the I/Ointerface 130 as external devices. In addition, FIG. 2 shows the examplein which the movement detection unit 171, the operation reception unit172, the display unit 173, and the audio output unit 174 are providedoutside the information processing device 100, but all or some of theunits may be installed inside the information processing device 100.

The movement detection unit 171 detects a movement of the informationprocessing device 100 by detecting acceleration, a motion, aninclination, or the like of the information processing device 100, andoutputs movement information regarding the detected movement to thecontrol unit 140 via the I/O interface 130. For example, the movementdetection unit 171 retains movement information which indicates whetheror not the information processing device 100 is moving to a differentplace (a log (or real-time information regarding the movement)), andsupplies the information to the control unit 140. As the movementdetection unit 171, for example, an acceleration sensor, a gyro sensor,or the Global Positioning System (GPS) can be used. The movementdetection unit 171 can compute a movement distance of the informationprocessing device 100 (for example, a movement distance per unit time)using, for example, position information (for example, latitude andlongitude) detected using the GPS.

The operation reception unit 172 is an operation reception unit whichreceives an operation input performed by a user, and outputs operationinformation according to the received operation input to the controlunit 140 via the I/O interface 130. The operation reception unit 172 isrealized with, for example, a touch panel, a keyboard, or a mouse.

The display unit 173 is a display unit on which various kinds ofinformation are displayed based on control of the control unit 140. Asthe display unit 173, for example, a display panel such as an organicelectro luminescence (EL) panel, or a liquid crystal display (LCD) canbe used. The operation reception unit 172 and the display unit 173 canbe configured to be integrated using a touch panel on which operationscan be input by a user bringing his or her finger in contact with orclose to its display plane.

The audio output unit 174 is an audio output unit (for example, aspeaker) which outputs various kinds of sounds based on control of thecontrol unit 140.

The control unit 140 controls each unit of the information processingdevice 100 based on a control program stored in the memory 150. Thecontrol unit 140 performs, for example, signal processing of transmittedand received information. In addition, the control unit 140 is realizedwith a central processing unit (CPU).

The memory 150 is a memory which stores various kinds of information.For example, the memory 150 stores various kinds of informationnecessary for the information processing device 100 to perform a desiredoperation (for example, the control program). In addition, the memory150 stores, for example, the mesh path table 350 shown in FIG. 11.Furthermore, the memory 150 stores various kinds of content such asmusic content and image content (for example, dynamic image content andstill image content).

When data is transmitted using wireless communication, for example, thecontrol unit 140 processes information read from the memory 150, asignal input from the I/O interface 130, or the like, and generates amass of data to be actually transmitted (transmission packets).Successively, the control unit 140 outputs the generated transmissionpackets to the communication unit 120. In addition, the communicationunit 120 converts the transmission packets in a format of acommunication scheme for actual transfer or the like, and transmits theconverted transmission packets to the outside from the antenna 110.

In addition, when data is received using wireless communication, forexample, the communication unit 120 extracts reception packets of radiowaves received via the antenna 110 through signal processing performedby a receiver inside the communication unit 120. Then, the control unit140 analyzes the extracted reception packets. When the packets aredetermined to be data to be retained as a result of the analysis, thecontrol unit 140 writes the data in the memory 150. In addition, whenthe packets are determined to be data to be transferred to anotherinformation processing device, the control unit 140 outputs the data tothe communication unit 120 as transmission packets to be transmitted toanother information processing device. Furthermore, when the packets aredetermined to be data to be transferred to an external actuator, thecontrol unit 140 outputs the packets to the outside (for example, thedisplay unit 173) from the I/O interface 130.

The control unit 140 can, for example, provide various kinds of contentstored in the memory 150 to another information processing device usingwireless communication.

It should be noted that, when the information processing device 100 isdriven by a battery, a battery is mounted (installed or loaded) in theinformation processing device 100. In this case, the control unit 140has a function of estimating a remaining battery amount, and thus canacquire the estimated remaining battery amount as needed.

[Example of a Signal Format]

FIG. 3 is a diagram showing an example of a signal format of a packetexchanged between information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology.

Here, each of the information processing devices constituting thecommunication system 200 exchanges signals in a packet form duringcommunication. The signal in the packet form includes at least two typesincluding a management packet and a data packet. Thus, a of FIG. 3 showsan example of the signal format of a management packet and b of FIG. 3shows the signal format of a data packet.

The management packet shown in a of FIG. 3 is a packet used forgenerating and retaining a network.

As shown in a of FIG. 3, the transmission signal of the managementpacket is composed of a header part (301 to 303) and a payload part 304.In addition, there are three fields in the header part. These threefields are a Frame Control field 301, an RX STA ADDR field 302, and a TXSTA ADDR field 303.

In the leading part of the header part, there is the Frame Control field301 in which an attribute of a signal including this header and the likeare stored. Each information processing device can acquire informationof whether a packet is a data packet or a management packet for controland management and the like with reference to the Frame Control field301.

In the RX STA ADDR field 302, an identifier (address) indicating apacket receiving station is stored. Each information processing devicecan know which information processing device is supposed to receive thesignal (packet) with reference to the RX STA ADDR field 302. Aninformation processing device which has received the signal (packet)starts a reception process of the received signal (packet) when, forexample, content of the RX STA ADDR field 302 is its own identifier(address) or a broadcast address.

In the TX STA ADDR field 303, an identifier (address) of a packettransmitting station. Each information processing device can recognizewhich information processing device has transmitted the signal withreference to the TX STA ADDR field 303.

The data packet shown in b of FIG. 3 is a packet used when applicationdata or the like is transmitted.

As shown in b of FIG. 3, the transmission signal of the data packet iscomposed of a header part (305 to 309) and a payload part 310. Inaddition, there are 5 fields in the header part. These 5 fields are aFrame Control field 305, an RX STA ADDR field 306, a TX STA ADDR field307, a Dst STA ADDR field 308, and an Src STA ADDR field 309.

In the leading part of the header part, there is the Frame Control field305 in which an attribute of a signal including this header and the likeare stored. Each information processing device can acquire informationof whether a packet is a data packet or a management packet for controland management and the like with reference to the Frame Control field305.

In the RX STA ADDR field 306, an identifier (address) indicating apacket receiving station is stored. Each information processing devicecan know which information processing device is supposed to receive thesignal (packet) with reference to the RX STA ADDR field 306. Aninformation processing device which has received the signal (packet)starts a reception process of the received signal (packet) when, forexample, content of the RX STA ADDR field 306 is its own identifier(address) or a broadcast address.

In the TX STA ADDR field 307, an identifier (address) of a packettransmitting station. Each information processing device can recognizewhich information processing device has transmitted the signal withreference to the TX STA ADDR field 307.

In the Dst STA ADDR field 308, an identifier (address) indicating apacket destination station (an information processing device which issupposed to receive the packet in the end) is stored. Each informationprocessing device can know to which information processing device thesignal is supposed to be transmitted in the end with reference to theDst STA ADDR field 308. An information processing device which hasreceived the signal performs a transfer process to transmit the receivedsignal to a destination station when, for example, the Dst STA ADDRfield 308 does not include its own identifier (address).

In the Src STA ADDR field 309, an identifier (address) of a packettransmission source station (an information processing device whichfirst transmitted the packet first) is stored. For example, eachinformation processing device can recognize which information processingdevice has transmitted the signal with reference to the Src STA ADDRfield 309.

Here, when data destined for a specific information processing device istransferred through the above-described multi-hop relay, it is necessaryto decide a path on which the data is to be relayed before the data istransferred. This procedure is called path selection. In addition, inthis path selection, a communication path is decided by exchanging amanagement signal between information processing devices for selecting apath. It should be noted that a communication path on a mesh network iscalled a mesh path. In FIGS. 4 to 7, types and formats of managementsignals used for generating this mesh path are shown.

[Examples of Signal Formats]

FIG. 4 is a diagram showing an example of a signal format of amanagement packet exchanged between the information processing deviceswhich constitute the communication system 200 according to the firstembodiment of the present technology.

FIGS. 5 to 7 are diagrams showing examples of the content of the signalformats of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology. In otherwords, FIGS. 5 to 7 show the examples of the content of the signalformats of the management packets shown in FIG. 4.

a of FIG. 4 shows the management packet. This management packet is thesame as that of a of FIG. 3. As described above, the Frame Control field301 of the management packet stores the fact that the signal is amanagement packet.

b to d of FIG. 4 show a configuration example of the payload part 304 ofthe management packet shown in a of FIG. 4. Specifically, b of FIG. 4shows a configuration example of a case in which the management packetis an RANN (root announcement signal). In addition, c of FIG. 4 shows aconfiguration example of a case in which the management packet is a PREQ(path request signal). Also, d of FIG. 4 shows a configuration exampleof a case in which the management packet is a PREP (path reply signal).

The RANN (root announcement signal) shown in b of FIG. 4 is a signalused for proactively generating a mesh path regardless of presence oftransmission data. Here, the case in which a mesh path is proactivelygenerated is a case in which, regardless of necessity of data transfer,a mesh path between a specific information processing device and anotherinformation processing device on a network is generated beforehand.

As shown in b of FIG. 4, there are a plurality of fields (311 to 318) inthe RANN.

In the Length field 311, information indicating the length of thepayload is stored.

In the ActionType field 312, an identifier indicating that the signal isan RANN is stored. An information processing device which has receivedthe signal can recognize that the received signal is an RANN withreference to the ActionType field 312.

In the Flags field 313, an attribute of a transmission source station ofthe RANN (information processing device which has transmitted the RANNfirst) is stored. This attribute is information indicating, for example,a role of the information processing device. For example, when theinformation processing device which has transmitted the RANN first(transmission source station) is a device for causing anotherinformation processing device to be connected to the Internet, the Flagsfield 313 stores that fact.

In the OrigSTA field 314, an identifier (address) indicating whichinformation processing device is the transmission source station of theRANN (information processing device which has transmitted the RANNfirst) is stored. Here, although the RANN is transferred to a remotespot through multi-hop relay, an information processing device which hasreceived the RANN can recognize which information processing device isthe transmission source station of the received RANN with reference toOrigSTA field 314.

In the SeqNum field 315, an identifier for identifying the RANN isstored. For example, each time the RANN is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 315. In other words, as the RANN is regularly orirregularly transmitted from the transmission source station, aninformation processing device which has received the RANN can recognizewhether or not the received RANN is the same RANN as that receivedbefore with reference to the SeqNum field 315.

In the HopCount field 316, a numerical value indicating the number ofhops necessary for the RANN to be delivered from the transmission sourcestation (information processing device which has transmitted the RANNfirst) is stored. An information processing device which has receivedthe RANN transfers the received RANN in multi-hop, and an incrementedvalue is stored in the HopCount field 316 with each the transferprocess.

In the Metric field 317, a value indicating a metric value that wasnecessary for arrival of the RANN from the transmission source station(information processing device which has transmitted the RANN first) isstored. An information processing device which has received the RANNtransfers the received RANN in multi-hop, and the Metric field 317stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

Here, a metric value of a link between information processing devices isa value indicating, for example, at how many Mbps transfer is possibleon that link. In the IEEE standard 802.11-2012, for example, a metricvalue ca can be obtained from the following expression 1.

ca=[O+(Bt/r)]/[1/(1−ed)]  Expression 1

Here, r is a value indicating a data rate (Mb/s). In addition, of is avalue indicating a frame error rate. Further, Bt is a value indicating aframe size. Also, O is an intrinsic value of a physical layer (PHY).

In the Etc field 318, other management information is stored.

The PREQ (path request signal) shown in c of FIG. 4 is a signal used forrequesting generation of a mesh path destined for a specific informationprocessing device.

As shown in c of FIG. 4, there are a plurality of fields (319 to 328) inthe PREQ.

In the Length field 319, information indicating the length of thepayload is stored.

In the ActionType field 320, an identifier indicating that the signal isa PREQ is stored. An information processing device which has receivedthe signal can recognize that the received signal is a PREQ withreference to the ActionType field 320.

In the Flags field 321, information indicating whether the PREQ has beentransmitted triggered by reception of the RANN (whether this is aproactive mesh path generation process) is stored.

In the OrigSTA field 322, an identifier (address) indicating aninformation processing device serving as a requesting source of meshpath generation (transmission source station) is stored. Here, althoughthe PREQ is transferred to a remote spot through multi-hop relay, aninformation processing device which has received the PREQ can recognizewhich information processing device is the transmission source stationof the received PREQ with reference to the OrigSTA field 322.

In the DestSTA field 323, an identifier indicating an informationprocessing device serving as a request destination of mesh pathgeneration (destination station) is stored. When an informationprocessing device specified with the identifier stored in the DestSTAfield 323 (destination station) receives the PREQ, the device replieswith a PREP in response thereto. Accordingly, a bidirectional mesh pathis generated.

In the SeqNum field 324, an identifier for identifying the PREQ isstored. For example, each time the PREQ is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 324. In other words, there are cases in which, although thePREQ is transmitted from the transmission source station a plurality oftimes, an information processing device which has received the PREQ canrecognize whether or not the received PREQ is the same one as a PREQreceived before with reference to the SeqNum field 324.

In the HopCount field 325, a numerical value indicating the number ofhops necessary for the PREQ to be delivered from the transmission sourcestation (information processing device which has transmitted the PREQfirst) is stored. An information processing device which has receivedthe PREQ transfers the received PREQ in multi-hop, and an incrementedvalue is stored in the HopCount field 325 with each the transferprocess.

In the Metric field 326, a value indicating a metric value that wasnecessary for arrival of the PREQ from the transmission source station(information processing device which has transmitted the PREQ first) isstored. An information processing device which has received the PREQtransfers the received PREQ in multi-hop, and the Metric field 326stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

In the Lifetime field 327, information indicating a lifetime of a meshpath is stored. In other words, when a mesh path generation requestsucceeds, a valid mesh path (active mesh path) is generated, and a valuefor specifying the lifetime of the mesh path is stored in the Lifetimefield 327.

In the Etc field 328, other management information is stored.

The PREP (path reply signal) shown in d of FIG. 4 is a signal used forreply to a request to generate a mesh path destined for a specificinformation processing device.

As shown in d of FIG. 4, there are a plurality of fields (329 to 338) inthe PREP.

In the Length field 329, information indicating the length of thepayload is stored.

In the ActionType field 330, an identifier indicating that the signal isa PREP is stored. An information processing device which has receivedthe signal can recognize that the received signal is a PREP withreference to the ActionType field 330.

In the Flags field 331, an attribute of a transmission source station ofthe PREP (an information processing device which has transmitted thePREP first) is stored.

In the OrigSTA field 332, an identifier indicating an informationprocessing device serving as a requesting source for generating a meshpath is stored. Here, the identifier of the information processingdevice stored in the OrigSTA field 322 of the PREQ (transmission sourcestation of the PREQ) is transcribed in the OrigSTA field 332.

In the DestSTA field 333, an identifier indicating an informationprocessing device serving as a request destination for generation of themesh path is stored. Here, the identifier of the information processingdevice stored in the DestSTA field 323 of the PREQ (destination stationof the PREQ) is transcribed in the DestSTA field 333.

In the SeqNum field 334, an identifier for identifying the PREP isstored. For example, each time the PREP is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 334. In other words, there are cases in which, although thePREP is transmitted from the transmission source station a plurality oftimes, a destination station which has received the PREP can recognizewhether or not the received PREP is the same one as a PREP receivedbefore with reference to the SeqNum field 334.

In the HopCount field 335, a numerical value indicating the number ofhops necessary for the PREP to be delivered from the transmission sourcestation of the PREP is stored. An information processing device whichhas received the PREP transfers the received PREP in multiple-hop, andan incremented value is stored in the HopCount field 335 with eachtransfer process.

In the Metric field 336, a value indicating a metric value that wasnecessary for arrival of the PREP from the transmission source stationis stored. An information processing device which has received the PREPtransfers the received PREP in multi-hop, and the Metric field 336stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

In the Lifetime field 337, information indicating a lifetime of a meshpath is stored. In other words, when a mesh path generation requestsucceeds, a valid mesh path (active mesh path) is generated, and a valuefor designating the lifetime of the mesh path is stored in the Lifetimefield 337.

In the Etc field 338, other management information is stored.

The information processing devices constituting the communication system200 generate path information (also referred to as transfer informationor mesh path information) necessary during multi-hop communication byexchanging the RANN, the PREQ, and the PREP. For example, theinformation processing devices generates a multi-hop communication pathat a fixed time interval or irregularly by exchanging the RANN, thePREQ, and the PREP. In addition, the path information is pathinformation for specifying the next information processing device towhich packets should be transferred in order to deliver the packets to adestination information processing device. This path information isretained inside each information processing device as a mesh path table.In addition, when transmitting data packets to a specific informationprocessing device, each information processing device decides aninformation processing device to be designated as a receiving station totransmit the packets with reference to the mesh path table. In otherwords, when transmitting data packets to a specific informationprocessing device, each information processing device decides whatinformation processing device should be designated in the RX STA ADDRfield 302 to transmit the packets with reference to the mesh path table.This mesh path table will be described in detail with reference to FIGS.8, 11, and the like.

[Configuration Example of a Mesh Path Table]

FIG. 8 is a diagram schematically showing an example of a mesh pathtable (mesh path table 340) retained by each information processingdevice which constitutes the communication system 200 according to thefirst embodiment of the present technology.

a of FIG. 8 schematically shows a configuration of the mesh path table340, and b of FIG. 8 shows an example of the content of the mesh pathtable 340. Specifically, b of FIG. 8 shows an Index 346, a data name347, and a meaning 348 as the example of the content of the mesh pathtable 340.

As shown in a of FIG. 8, the mesh path table 340 is recorded in thememory 150 in a record form. In addition, the mesh path table 340 isdesigned such that each record can be extracted therefrom using theaddress (Dest 341) of a destination station as a key. In addition, asrecords of the mesh path table 340, a NextHop 342, a Metric 343, aSeqNum 344, and an ExpTime 345 are stored. It should be noted that, in bof FIG. 8, reference symbols a to d for identifying each of the recordsare given in the Index 346.

In the NextHop 342 of “a” of the Index 346, an identifier of aninformation processing device indicating to what information processingdevice data should be transferred next in order to deliver the data to adestination station is stored. In other words, the NextHop 342 stores anidentifier of a transmitting station.

In the Metric 343 of “b” of the Index 346, a path metric value from aself-station to the destination station of the mesh path is stored. Acomputation method for this path metric value will be shown in FIGS. 9,10, etc.

In the SeqNum 344 of “c” of the Index 346, the value of SeqNum of thePREQ or the PREP (for example, the SeqNum fields 324 and 334 shown in cand d of FIG. 4) used to generate the mesh path is stored.

In the ExpTime 345 of “d” of the Index 346, the expiration time of themesh path is stored. The expiration time of the mesh path is decidedbased on the Lifetime fields 327 and 337 of the PREQ or the PREP (shownin c and d of FIG. 4) used to generate the mesh path.

Each information processing device constituting the communication system200 generates path information at the time of a request of generation ofa path or a reply thereto, and writes the generated path information inthe mesh path table 340. In addition, when transferring data, based onthe address (Dest 341) of a destination station to which the data is tobe delivered, each information processing device constituting thecommunication system 200 extracts a record corresponding to thedestination station from the mesh path table 340. In addition, theinformation processing device performs a transfer process fortransferring the data to a transmitting station corresponding to theNextHop 342 of the extracted record.

[Generation Example of a Mesh Path]

FIGS. 9 and 10 are diagrams showing a generation example of a mesh pathretained by each information processing device constituting thecommunication system 200 according to the first embodiment of thepresent technology.

In FIGS. 9 and 10, the procedure for generating the mesh path table 340using a PREQ and a PREP will be described. Specifically, in FIGS. 9 and10, a case in which, when the information processing device 100 attemptsto transmit data destined for the information processing device 240 inthe topology shown in FIG. 1, the information processing device 100requests generation of a mesh path between the information processingdevice 240 will be described.

As shown in a of FIG. 9, the information processing device 100 transmitsa PREQ in which the information processing device 240 has beendesignated in the Dest STA field 323 (shown in c of FIG. 4). Aconfiguration of the PREQ has been shown in c of FIG. 4 and FIG. 6. Inaddition, when the PREQ is transmitted, the control unit 140 of theinformation processing device 100 stores zero as an initial value in theHopCount field 325 and the Metric field 326 of the PREQ to betransmitted. Furthermore, the control unit 140 of the informationprocessing device 100 stores a value obtained by incrementing the valuestored in the PREQ that was transmitted the previous time in the SeqNumfield 324 of the PREQ to be transmitted. In addition, the control unit140 of the information processing device 100 sets a broadcast addressfor designating each information processing device located nearby as areceiving station in the RX STA ADDR field 303 (shown in a of FIG. 4) ofthe management packet of the PREQ to be transmitted.

It should be noted that, in a of FIG. 9, the flow of the PREQtransmitted from the information processing device 100 to eachinformation processing device is schematically shown with thick-linearrows. In addition, the name of the signal (PREQ), the reference symbolof the destination station (Dest=E), and the reference symbol of thetransmission source station and relay station (including thetransmitting station) of the PREQ (A) are given to the thick-linearrows.

For example, PREQ Dest=E(A) shown in a of FIG. 9 means that it is a PREQof which the destination station is the information processing device240 and the transmission source station and the relay station (includingthe transmitting station) are the information processing device 100. Itshould be noted that the same applies to the names and reference symbolsof thick-line arrows in the following drawings.

As shown in a of FIG. 9, the information processing devices 210, 220,and 230 receive the PREQ transmitted from the information processingdevice 100. Upon receiving the PREQ, the information processing devices210, 220, and 230 generate path information destined for an informationprocessing device (destined for the information processing device 100)of which the identifier is stored in the OrigSTA field 322 of thereceived PREQ. In addition, the information processing devices 210, 220,and 230 records the generated path information in the mesh path table340 as path information destined for the information processing device100.

In this case, each information processing device stores the identifier(address) of the information processing device 100 in the Dest 341 ofthe mesh path table 340. In addition, each information processing devicestores the identifier (address) of the TX STA ADDR field 303 of thereceived PREQ in the NextHop 342 of “a” of the Index 346 of the meshpath table 340.

Furthermore, each of the information processing devices acquires ametric value of a link between a transmitting station of the receivedPREQ and the self-device. For example, the information processing device210 acquires a metric value of a link between the transmitting station(the information processing device 100) of the received PREQ and theself-device (the information processing device 210). Subsequently, eachinformation processing device computes a path metric value by adding theacquired metric value of the link to the value stored in the Metricfield 326 of the received PREQ. Then, each information processing devicestores the computed path metric value in the Metric 343 of “b” of theIndex 346 of the mesh path table 340.

Here, the transmitting station of the received PREQ is the informationprocessing device corresponding to the identifier stored in the TX STAADDR field 303, and is the information processing device 100 in theexample shown in FIG. 9. In addition, the metric value of the linkbetween the transmitting station of the received PREQ and theself-device is, for example, a value which indicates at how many Mbpstransfer is possible on that link.

Furthermore, each information processing device stores the value of theSeqNum field 324 of the received PREQ in the SeqNum 344 of “c” of theIndex 346 of the mesh path table 340.

In addition, each information processing device stores the valueobtained by adding the value stored in the Lifetime field 327 of thePREQ to the reception time of the PREQ (expiration time) in the ExpTime345 of “d” of the Index 346 of the mesh path table 340. The mesh pathgenerated in that manner is referred to as a value mesh path until theexpiration time stored in the ExpTime 345 of “d” of the Index 346 of themesh path table 340.

In this manner, the information processing devices 210, 220, and 230generate the mesh path destined for the information processing device100.

Furthermore, as shown in b of FIG. 9, the respective informationprocessing devices 210, 220, and 230 which have received the PREQtransfer the received PREQ because the identifier of the DestSTA field323 of the received PREQ is not theirs. At the time of this transfer,the information processing devices 210, 220, and 230 increment the valueof the HopCount field 325 of the received PREQ. Then, the previouslycalculated path metric value is stored in the Metric field 326, and thevalue of the received PREQ is transcribed in the field of another PREQ.In addition, the information processing devices 210, 220, and 230 set abroadcast address for designating each information processing devicelocated nearby as a receiving station in the RX STA ADDR field 302.

Upon receiving the transferred PREQ, for example, the informationprocessing device 240 generates path information destined for theinformation processing device (destined for the information processingdevice 100) of which the identifier is stored in the OrigSTA field 322of the received PREQ in the above-described procedure. Then, theinformation processing device 240 records the generated path informationin the mesh path table 340 as path information of which the recipient isset to the information processing device 100.

Here, as shown in b of FIG. 9, the information processing device 240receives such PREQ from the information processing devices 220 and 230.When the PREQ has received from a plurality of information processingdevices in this manner, the information processing device 240 selects apath having a low path metric value as a valid mesh path, and discards aPREQ having a high path metric value.

In the example shown in FIG. 9, a case in which the path metric value ofthe PREQ transferred from the information processing device 230 is lowerthan the path metric value of the PREQ transferred from the informationprocessing device 220 is assumed. In this case, the informationprocessing device 240 generates a mesh path of which the NextHop 342 isset to the information processing device 230 as a mesh path designed forthe information processing device 100.

In addition, since the information processing device 240 designatesself-device as the DestSTA field 323 of the received PREQ, the devicegenerates a PREP for replying to this PREQ. Thus, as shown in a of FIG.10, the information processing device 240 transmits the generated PREPby designating the NextHop destined for the OrigSTA field 322 of thePREQ as a receiving station.

In this case, the information processing device 240 transcribes thevalues stored in the PREQ in the OrigSTA field 332 and the DestSTA field333, and stores zero as an initial value in the HopCount field 335 andthe Metric field 336. In addition, the information processing device 240stores in the SeqNum 344 the value obtained by incrementing the valuestored in the previously transmitted PREQ or PREP. In addition, theinformation processing device 240 sets the NextHop destined for OrigSTAof the PREQ (the information processing device 230 in this case) in theRX STA ADDR field 302 for transmission to the information processingdevice 230 in unicast.

Upon receiving the PREP transmitted from the information processingdevice 240, the information processing device 230 generates pathinformation destined for an information processing device (destined forthe information processing device 240) of which the identifier is storedin the DestSTA field 333 of the received PREP in the above-describedprocedure. Then, the information processing device 230 records thegenerated path information in the mesh path table 340 as pathinformation of which the destination is set to the informationprocessing device 240. In this manner, upon receiving the PREPtransmitted from the information processing device 240, the informationprocessing device 230 generates a mesh path destined for the informationprocessing device 240.

As shown in b of FIG. 10, the identifier of the OrigSTA field 332 of thereceived PREP is not of the information processing device 230 which hasreceived the PREP. For this reason, the information processing device230 transfers the received PREP to the information processing devicewhich corresponds to the identifier of the OrigSTA field 332 of thereceived PREP. At the time of this transfer, the information processingdevice 230 increments the value of the HopCount field 335 of thereceived PREP. Then, a path metric value calculated in theabove-described procedure is stored by the information processing device203 in the Metric field 336, and the value of the received PREP istranscribed in the field of another PREP. In addition, in order totransmit the PREP in unicast, the information processing device 230 setsthe address of the NextHop 342 of the mesh path destined for theinformation processing device 100 (the address of the informationprocessing device 100) in the RX STA ADDR field 302. Accordingly,unicast transmission of the PREP from the information processing device230 to the information processing device 100 is performed as shown in bof FIG. 10.

Upon receiving the PREP transmitted from the information processingdevice 230, the information processing device 100 generates pathinformation destined for the information processing device of which theidentifier is stored in the DestSTA field 333 of the received PREP(destined for the information processing device 240) in theabove-described procedure. Then, the information processing device 100records the generated path information in the mesh path table 340 aspath information of which the destination is set to the informationprocessing device 240.

In this manner, the information processing device 100 generates a meshpath destined for the information processing device 240. In addition,since the identifier of the OrigSTA field 332 of the received PREP is ofthe information processing device 100, the device finishes thebi-directional mesh path generation procedure between the informationprocessing device 100 and the information processing device 240 withoutperforming a successive transfer process.

Thereafter, the mesh path records generated and retained in each of theinformation processing devices can be referred to before the expirationtime (ExpTime 345) of the generated mesh path elapses. For this reason,before the expiration time elapses, when data is exchanged between theinformation processing device 100 and the information processing device240, the mesh path records retained in each of the informationprocessing devices can be referred to to perform communication inmulti-hop relay.

When there is a mesh path of which the expiration time has arrived, eachinformation processing device destroys the mesh path of which theexpiration time has arrived, and re-generates a mesh path destined forthe information processing device of which the expiration time hasarrived.

It should be noted that, although the mesh path can be generated byexchanging another signal (for example, RANN), description thereof isomitted here.

[Regarding Generation and Maintenance Management of a Mesh Path]

As described above, each of the information processing devices whichconstitute the communication system 200 exchanges signals (PREQ, PREP,and RANN) to generate and perform maintenance management of a mesh path.Thus, it is important to more appropriately perform generation andmaintenance management of a mesh path by making a change or addition toeach of the processes. This point will be described below.

[Regarding a Mesh Path Updating Timing]

When there is a mesh path of which the expiration time has arrived, eachof the information processing devices which constitute the communicationsystem 200 destroys the mesh path (path information) of which theexpiration time has arrived, as described above. Thus, it is notpossible to transmit a next data packet for the time until a mesh pathis generated again.

Thus, in the first embodiment of the present technology, an example inwhich a mesh path is updated before the mesh path is destroyed will beshown.

[Regarding a Mesh Path Updating Timing]

When there is a mesh path of which the expiration time has arrived, eachof the information processing devices which constitute the communicationsystem 200 destroys the mesh path of which the expiration time hasarrived, as described above. Then, generation of a mesh path to adestination station is started. In this case, because a number of PREQsand PREPs are transmitted from the plurality of information processingdevices substantially at the same timing, there is concern of radiowaves being congested.

Therefore, in the first embodiment of the present technology, an examplein which different mesh path generation timings are set for theplurality of information processing devices will be shown.

[Regarding a Value of LifeTime]

Here, a situation of a mesh path is assumed to change due to movement ofan information processing device, appearance of a new informationprocessing device, or the like. However, when a situation of a mesh pathis not likely to change, for example, if a value of LifeTime isconstant, there is concern of the mesh path being unnecessarily updated.On the other hand, when a situation of a mesh path is likely to change,if the value of LifeTime is constant, there is concern of updating ofthe mesh path being delayed. Thus, it is important to appropriatelyupdate a mesh path by appropriately setting the value of LifeTime.

Therefore, in the first embodiment of the present technology, an examplein which the value of LifeTime is changed according to a state (forexample, a movement state, or a communication state) of an informationprocessing device will be shown.

[Regarding a Metric Value]

The metric value ca can be obtained using the following Expression 1 in,for example, the IEEE 802.11-2012 standard, as described above.

ca=[O±(Bt/r)]/[1/(1−ef)]  Expression 1

Here, when there is no data communication performed for a long period oftime, there are cases in which a data rate is not updated and it is notpossible to deal with a change in a situation. In addition, when datacommunication is performed only for obtaining a metric value,unnecessary traffic occurs.

Thus, in a second embodiment of the present technology, an example inwhich a metric value is obtained by appropriately using an error ratewill be shown.

[Regarding Comparison of Metric Values when a Mesh Path is to beSelected]

A case in which, when a mesh path is to be selected, the metric valuesof two or more paths are similar is also assumed. In such a case, thereis concern of paths being switched each time a mesh path is switched andparameters which are affected by the paths being easily changed.

Therefore, in the second embodiment of the present technology, anexample in which frequent switching of mesh paths is prevented byapplying hysteresis to selection of a mesh path will be shown.

It should be noted that, as a technology for configuring such a wirelessnetwork system described above, the IEEE standard 802.11-2012 (IEEEStandard for Information Technology—Telecommunications and informationexchange between systems—Local and metropolitan area networks—Specificrequirements Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications) is widely known.

[Configuration Example of a Mesh Path Table]

FIG. 11 is a diagram schematically showing an example of a mesh pathtable (mesh path table 350) retained by each information processingdevice which constitutes the communication system 200 according to thefirst embodiment of the present technology.

a of FIG. 11 schematically shows a configuration of a mesh path table350, and b of FIG. 11 shows an example of the content of the mesh pathtable 350. Specifically, in b of FIG. 11, the Index 346, the data name347, and the meaning 348 are shown as the example of the content of themesh path table 350. It should be noted that the mesh path table 350shown in a and b of FIG. 11 is obtained by changing a part of the meshpath table 340 shown in FIG. 8 and adding new information thereto.Specifically, it is information in which the mesh path expiration timeof ExpTime 345 indicated by reference symbol d is set for an updatingexpiration time for a mesh path and information of reference symbols eand f are newly added. Thus, same reference symbols are given toportions of a and b of FIG. 11 which are the same as those in the meshpath table 340 shown in a and b of FIG. 8 and a part of descriptionthereof will be omitted. In addition, a of FIG. 11 corresponds to a ofFIG. 8, and b of FIG. 11 to b of FIG. 8.

As shown in FIG. 11a , the mesh path table 350 is recorded in the memory150 in a record form. For the sake of facilitating description in theembodiment of the present technology, an example in which the mesh pathtable 350 produced by adding new information to the mesh path table 340shown in FIG. 8 is managed as one table is shown. The newly addedinformation (the information of the reference symbols e and f), however,may be managed as a separate table (or in a separate memory) from themesh path table 340.

In the ExpTime ((ExpireTime)) 345 of “d” of the Index 346, an updatingexpiration time of the mesh path is stored. This updating expirationtime of the mesh path is decided based on the LifeTime fields 327 and337 (shown in c and d of FIG. 4) of a PREQ or a PREP used in generationof the mesh path.

In the LifeTime 351 of “e” of the Index 346, a lifetime of the mesh pathis stored. The lifetime of the mesh path is decided based on theLifeTime fields 327 and 337 (shown in c and d of FIG. 4) of the PREQ orthe PREP used in generation of the mesh path.

In the HopCount 352 of “f” of the Index 346, a numerical valueindicating the number of hops necessary for delivering a PREP from atransmission source station (an information processing device which hastransmitted the PREP first).

[Example in which ExpTime is to Set to be Shorter than LifeTime]

FIG. 12 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology. This generation and updatingwill be described in detail with reference to FIGS. 9 and 10.

In addition, in this example, an example in which a value of the ExpTime345 (“d” of the Index 346) (updating expiration time of the mesh path)of the mesh path table 350 shown in FIG. 11 is set to be shorter than avalue of LifeTime (“e” of the Index 346) (lifetime of the mesh path) isshown.

Here, a case in which, when the information processing device 100transmits data to the information processing device 240, the informationprocessing device 100 requests generation of a mesh path between theinformation processing device 240 will be described with reference toFIGS. 9 and 10.

As shown in a of FIG. 9, the information processing device 100 transmitsa PREQ in which the information processing device 240 is designated inthe DestSTA field 323 (shown in c of FIG. 4). This PREQ is the same asin the example shown in a of FIG. 9, and thus description thereof willbe omitted here.

In addition, when there is no mesh path destined for the informationprocessing device 240, the control unit 140 of the informationprocessing device 100 generates path information of which thedestination is the destination station of the PREQ. Here, thedestination station of the PREQ is the information processing device ofwhich the identifier is stored in the DestSTA field 323 (shown in c ofFIG. 4), which is the information processing device 240 in this example.

For example, the control unit 140 of the information processing device100 stores the identifier of the information processing device 240 inthe Dest 341 as shown in a of FIG. 12. In addition, the control unit 140of the information processing device 100 stores the sum of the currenttime (transmission time of the PREQ) and the value (T1) stored in theLifeTime field 327 of the PREQ in the LifeTime 351 (“e” of the Index346).

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T1 in the ExpTime 345(“d” of the Index 346).

Here, when the value stored in the LifeTime field 327 of the PREQ is setto T1, T2 is a value satisfying the following condition.

T1>T2>0

In addition, the control unit 140 of the information processing device100 stores the value obtained by adding 1 to the value of the SeqNumfield 324 of the PREQ which has been transmitted in the previous roundin the SeqNum 344 (“c” of the Index 346).

In addition, the control unit 140 of the information processing device100 leaves each of the NextHop 342 (“a” of the Index 346), the Metric343 (“b” of the Index 346), and the HopCount 352 (“f” of the Index 346)undefined.

In this manner, the control unit 140 of the information processingdevice 100 generates a mesh path destined for the information processingdevice 240.

In addition, as shown in a of FIG. 9, the information processing devices210, 220, and 230 receive the PREQ transmitted from the informationprocessing device 100. Upon receiving the PREQ as above, the informationprocessing devices 210, 220, and 230 generate path information destinedfor the information processing device (destined for the informationprocessing device 100) of which the identifier is stored in the OrigSTAfield 322 of the received PREQ. In other words, the informationprocessing devices 210, 220, and 230 record the generated pathinformation in the mesh path table 350 as path information whosedestination is the information processing device 100.

As shown in b of FIG. 12, the identifier stored in the OrigSTA field 322(shown in c of FIG. 4) (the identifier of the information processingdevice 100) is stored in the Dest 341 of the mesh path table 350 of eachof the information processing devices. In addition, the content shown inb of FIG. 12 is stored in each of the NextHop 342, the Metric 343, andthe SeqNum 344 of “a” to “c” of the Index 346 of the mesh path table350.

In addition, each of the information processing devices stores thefollowing value in the LifeTime 351 of “e” of the Index 346 of the meshpath table 350 as shown in b of FIG. 12.

Reception Time of PREQ+T1(value stored in LifeTime field 327 of PREQ)

Here, when the time stored in the LifeTime 351 arrives, each of theinformation processing devices destroys the mesh path correspondingthereto and updates the destroyed mesh path. In other words, when thetime stored in the LifeTime 351 arrives, each of the informationprocessing devices destroys each record corresponding thereto amongrecords of the mesh path table 350, and updates the destroyed record.

In addition, each of the information processing devices stores thefollowing value in the ExpTime 345 of “d” of the Index 346 of the meshpath table 350 as shown in b of FIG. 12.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)−T2

In other words, T1−T2 is set in the ExpTime 345 of “d” of the Index 346of the mesh path table 350.

In addition, when the time stored in the ExpTime 345 arrives, each ofthe information processing devices updates the mesh path correspondingthereto. In other words, when the time stored in the ExpTime 345arrives, each of the information processing devices updates each recordcorresponding thereto among the records of the mesh path table 350.

In addition, each of the information processing devices stores the valuestored in the HopCount field 325 of the PREQ in the HopCount 352 of “f”of the Index 346 of the mesh path table 350 as shown in b of FIG. 12.

In this manner, each of the relay stations (the information processingdevices 210, 220, and 230) generates a mesh path destined for theinformation processing device 100.

In addition, each of the information processing devices 210, 220, and230 which have received the PREQ transfers the received PREQ as shown inb of FIG. 9 because the identifier in the DestSTA field 323 of thereceived PREQ is not its own identifier. Since this PREQ to betransferred is the same as in the example shown in b of FIG. 9,description thereof is omitted here.

Upon receiving the PREQ transferred as above, for example, theinformation processing device 240 generates path information destinedfor the information processing device (destined for the informationprocessing device 100) of which the identifier is stored in the OrigSTAfield 322 of the received PREQ in the above-described procedure. Inother words, the information processing device 240 records the generatedpath information in the mesh path table 350 as path information whosedestination is the information processing device 100.

Here, the information processing device 240 receives the PREQ from eachof the information processing devices 220 and 230 as shown in b of FIG.9. Upon receiving the PREQs from the plurality of information processingdevices, the information processing device 240 selects a path with a lowpath metric value as a valid mesh path, and discards the PREQ with ahigh path metric value.

In this example, the case in which the path metric value of the PREQtransferred from the information processing device 230 is lower than thepath metric value of the PREQ transferred from the informationprocessing device 220 is assumed as described above. Thus, theinformation processing device 240 generates a mesh path for which theNextHop 342 is set to the information processing device 230 as a meshpath destined for the information processing device 100.

In addition, since the information processing device 240 is designatedas the DestSTA field 323 of the received PREQ, the device itselfgenerates a PREP to respond to the PREQ. Then, the informationprocessing device 240 transmits the generated PREP by designating theNextHop destined for the OrigSTA field 322 of the PREQ as a receivingstation as shown in a of FIG. 10. Since the PREP generated in this caseas a transmission target is the same as in the example shown in a ofFIG. 10, description thereof is omitted here.

In addition, the identifier stored in the DestSTA field 323 (shown in cof FIG. 4) (the identifier of the information processing device 100) isstored in the Dest 341 of the mesh path table 350 of the informationprocessing device 240. In addition, the content shown in c of FIG. 12 isstored in each of the NextHop 342, the Metric 343, and the SeqNum 344 of“a” to “c” of the Index 346 of the mesh path table 350.

In addition, the information processing device 240 stores the followingvalue in the LifeTime 351 of “e” of the Index 346 of the mesh path table350 as shown in c of FIG. 12.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)

In addition, the information processing device 240 stores the followingvalue in the ExpTime 345 of “d” of the Index 346 of the mesh path table350 as shown in c of FIG. 12.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)−T2

In addition, when the time stored in the LifeTime 351 arrives, theinformation processing device 240 destroys the mesh path correspondingthereto and updates the destroyed mesh path as described above. Inaddition, when the time stored in the ExpTime 345 arrives, theinformation processing device 240 updates the mesh path correspondingthereto.

In addition, the information processing device 240 stores the valuestored in the HopCount field 325 of the PREQ in the HopCount 352 of “f”of the Index 346 of the mesh path table 350 as shown in c of FIG. 12.

In addition, the information processing device 240 transmits thegenerated PREP by designating the NextHop 342 destined for the OrigSTAfield 322 of the PREQ as a receiving station. Since the PREP generatedin this case as a transmission target is the same as in the exampleshown in a of FIG. 10, description thereof is omitted here.

In addition, since generation of a mesh path of each of the informationprocessing devices which have received the PREP is the same as in theexample shown in a and b of FIG. 10 except for the point that thecontent of “d” to “f” of the Index 346 of the mesh path table 350 isdifferent, description thereof is omitted here. In addition, since thecontent of “d” to “f” of the Index 346 of the mesh path table 350 is thesame as in the example of each of the information processing deviceswhich has received the above-described PREQ, description thereof isomitted here.

Each of the information processing devices updates the content of themesh path table 350 as described above. In addition, when the timestored in the LifeTime 351 arrives, each of the information processingdevices destroys the mesh path corresponding thereto and updates thedestroyed mesh path. However, at the timing at which the earlier timethan the time stored in the LifeTime 351 (the time stored in the ExpTime345) has arrived, each of the information processing devices can updatethe mesh path corresponding thereto.

In other words, before the path information regarding the mesh path(communication path) set through exchange of the signals such as thePREQ and the PREP is destroyed, the control unit 140 performs control toupdate the path information. Specifically, the control unit 140 decidesan effective time (expiration time) for specifying a time at which thepath information is destroyed based on expiration time informationincluded in the signals such as the PREQ and the PREP. In addition,based on the expiration time information included in the signals such asthe PREQ and the PREP, the control unit 140 decides an updating time(updating expiration time) for specifying a time during which the pathinformation is updated to be a time shorter than the effective time.

Accordingly, when a multi-hop communication path is generated throughthe exchange of the signals such as the PREQ and PREP, updating of amesh path that has already been generated (path information) can bestarted before the mesh path is destroyed.

[Example in which ExpTime is Changed According to a Position on a Path]

The example in which ExpTime is set to be shorter than LifeTime has beenshown above. Here, an example in which ExpTime is changed according to aposition on a path will be shown. For example, an interval of updatingtimes of a transmission source station which has transmitted a pathsetting request (for example, a PREQ) first is set to be the shortest,and an interval of updating times of a destination station of the pathsetting request is set to be the second shortest. Furthermore, intervalsof updating times of relay stations are set to be shorter according totheir positions in the order of hopping from the transmission sourcestation.

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Specifically, the generated content (orupdated content) of the ExpTime 345 (“d” of the Index 346) of the meshpath table 350 is different. Thus, the difference will be mainlydescribed below, and a part of description regarding common portions tothe above-described example will be omitted.

FIGS. 13 and 14 are diagrams showing generation and updating examples ofthe mesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology. It should be noted that a ofFIG. 13 is the same as the example shown in a of FIG. 12.

Each of relay stations (the information processing devices 210, 220, and230) stores the next value in the ExpTime 345 of “d” of the Index 346 ofthe mesh path table 350 as shown in b of FIG. 13.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)−T5

Here, when the value stored in the LifeTime field 327 of the PREQ is setto T1, T5 is a value which satisfies the following condition.

T1>T2>T3>T4≧T5>0

It should be noted that T3 and T4 will be shown below.

As described above, each of the relay stations (the informationprocessing devices 210, 220, and 230) generates a mesh path destined forthe information processing device 100.

In addition, the destination station (the information processing device240) stores the following value in the ExpTime 345 of “d” of the Index346 of the mesh path table 350.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)−T3

Here, when the value stored in the LifeTime field 327 of the PREQ is setto T1, T3 is a value which satisfies the above condition(T1>T2>T3>T4≧T5>0).

In addition, the information processing device 240 transmits thegenerated PREP by designating the NextHop 342 destined for the OrigSTAfield 322 of the PREQ as a receiving station. Since the PREP generatedto be transmitted in this case is the same as in the example shown in aof FIG. 10, description thereof is omitted here.

In addition, generation of a mesh path of the relay station (theinformation processing device 230) which has received the PREP from theinformation processing device 240 is the same as in the example shown ina and b of FIG. 10 except for the point that the content of the ExpTime345 (“d” of the Index 346) is different.

Specifically, the relay station (the information processing device 230)stores the following value in the ExpTime 345 of “d” of the Index 346 ofthe mesh path table 350 as shown in FIG. 14.

Reception time of PREP+T1(value stored in LifeTime field 337 of PREP)−T4

Here, when the value stored in the LifeTime field 337 of the PREQ isassumed to be T1, T4 is a value satisfying the above-described condition(T1>T2>T3>T4≧T5>0) and the following conditions.

T4=T3−T5×HopCount(if(T3−T5×(PREP HopCount+1))>T5)

T4=T5(if(T3−T5×(PREP HopCount+1))≦T5)

As described above, the control unit 140 changes an updating time(updating period) of a mesh path (communication path) based on theposition of the information processing device 100 on the mesh path(communication path). In this case, when the information processingdevice 100 is an information processing device located at an end of themesh path (communication path), the control unit 140 sets the updatingtime (updating expiration time) to be shorter than that of anotherinformation processing device on the mesh path (communication path).Specifically, the control unit 140 sets the updating time (updatingexpiration time) to be the shortest when the information processingdevice 100 is the transmission source station, and sets the updatingtime (updating expiration time) to be the second shortest when theinformation processing device 100 is the destination station.

In this manner, for example, the interval of the updating time of thetransmission source station which has transmitted the path settingrequest (for example, a PREQ) first is set to be the shortest, and theinterval of the updating time of the destination station of the pathsetting request is set to be the second shortest. In addition, forexample, the interval of the updating time of the relay stations can beset to be shorter according to the orders of hops of the relay stationsfrom the transmission source station.

[Example in which LifeTime is Changed According to the Total Number ofHops]

The example in which ExpTime is changed according to a position on apath has been shown above. Here, an example in which LifeTime is changedaccording to the total number of hops will be shown.

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Specifically, the content of generation (orcontent of updating) of the ExpTime 345 (“d” of the Index 346) and theLifeTime 351 (“e” of the Index 346) of the mesh path table 350 isdifferent. Thus, the differences will be mainly described below, and apart of description regarding common portions to the above-describedexample will be omitted.

FIGS. 15 and 16 are diagrams showing generation and updating examples ofthe mesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

As shown in a of FIG. 9, the information processing device 100 transmitsthe PREQ for which the information processing device 240 is designatedin the DestSTA field 323 (shown in c of FIG. 4). In this case, whenthere is no mesh path destined for the information processing device240, the control unit 140 of the information processing device 100generates path information of which the destination is set to thedestination station of the PREQ.

As shown in a of FIG. 15, for example, the control unit 140 of theinformation processing device 100 stores the sum of the current time(transmission time of the PREQ) and T6 in the LifeTime 351 (“e” of theIndex 346).

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T6 in the ExpTime 345(“d” of the Index 346).

Here, when the value stored in the LifeTime field 327 of the PREQ isassumed to be T1, T6 is the value satisfying the following condition.

T6=T1>T2>0

In this manner, the control unit 140 of the information processingdevice 100 generates a mesh path destined for the information processingdevice 240.

In addition, when there is a mesh path destined for the informationprocessing device 240, the value of T6 may be changed according to thevalue of the HopCount 352 as shown in the following Expression 2.

T6=T5×(HopCount+1)  Expression 2

In this case, in order to prevent the value of ExpTime 345 from beingexcessively short, an upper limit may be set for the value of T6.

In this manner, the control unit 140 of the information processingdevice 100 updates the mesh path destined for the information processingdevice 240.

Each of the relay stations (information processing devices 210, 220, and230) stores the following value in the ExpTime 345 of “d” of the Index346 of the mesh path table 350 as shown in b of FIG. 15.

Reception time of PREQ+T1(value stored in LifeTime field 327 of PREQ)−T5

Here, when the value stored in the LifeTime field 327 of the PREQ isassumed to be T1, T5 is a value satisfying the following condition.

T6>T2>T3>T4≧T5>0

In this manner, each of the relay stations (information processingdevices 210, 220, and 230) generates a mesh path destined for theinformation processing device 100.

In addition, the destination station (information processing device 240)stores the following value in the ExpTime 345 of “d” of the Index 346 ofthe mesh path table 350.

Reception time of PREQ+T1(value stored in the LifeTime field 327 ofPREQ)−T3

Here, T3 may be changed according to the value of T6. For example, T3=T7(a constant) is possible.

In addition, the information processing device 240 transmits thegenerated PREP by designating the NextHop 342 destined for the OrigSTAfield 322 of the PREQ as a receiving station. Since the PREP generatedto be transmitted in this case is the same as in the example shown in aof FIG. 10, description thereof is omitted here.

In addition, generation of a mesh path by a relay station (informationprocessing device 230) which has received the PREP from the informationprocessing device 240 is the same as in the example shown in a and b ofFIG. 10 except for the point that the content of the ExpTime 345 (“d” ofthe Index 346) is different.

Specifically, the relay station (information processing device 230)stores the following value in the ExpTime 345 of “d” of the Index 346 ofthe mesh path table 350 as shown in FIG. 16.

Reception time of PREP+T1(value stored in the LifeTime field 337 of thePREP)−T4

Here, T4 is set to be a value satisfying the above-described condition(T6>T2>T3>T4≧T5>0) and the following conditions.

T4=T3−T5×HopCount(if(T3−T5×(PREP HopCount+1))>T5)

T4=T5(if(T3−T5×(PREP HopCount+1))≦T5)

In this manner, the control unit 140 changes the lifetime (expirationtime) of the mesh path (communication path) based on the number of relaystations.

[Example in which the LifeTime is Changed According to a Situation of aPath]

The example in which the ExpTime is changed has been shown above.

Here, an example in which the LifeTime is changed according to asituation of a path will be shown. When a situation of a path is notchanged (for example, adjacent similar information processing devicesare consecutively selected), for example, a value of the LifeTime can beincreased (the expiration time can be extended).

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Thus, the differences will be mainly describedbelow, and a part of description regarding common portions to theabove-described example will be omitted.

[Configuration Example of a Mesh Path Table]

FIG. 17 is a diagram schematically showing still another example of themesh path table (mesh path table 360) retained by each of theinformation processing devices which constitute the communication system200 according to the first embodiment of the present technology. Since aconfiguration of the mesh path table 360 has the same form as in theexample shown in a of FIG. 11, illustration thereof is omitted here.

In addition, in FIG. 17, the Index 346, the data name 347, and themeaning 348 are shown as examples of the content of the mesh path table360. The mesh path table 360 shown in FIG. 17 is obtained by adding newinformation to the mesh path table 350 shown in FIG. 11. Specifically,information of reference symbols a-1 to a-9 is newly added information.Thus, in FIG. 17, the same reference symbols are given to portionscommon to those of the mesh path table 350 shown in FIG. 11 and part ofdescription thereof will be omitted. Furthermore, FIG. 17 corresponds tob of FIG. 11.

In a NextHop-1 (361) of “a-1” of the Index 346, the identifier of theNextHop 342 of “a” of the Index 346 stored just before is stored. Inother words, in the NextHop-1 (361) of “a-1” of the Index 346, theidentifier of the NextHop 342 of 1 previous communication is stored.

Likewise in a NextHop-2 (362) to a NextHop-9 (369) of “a-2” to “a-9” ofthe Index 346, the identifiers of the NextHop 342 of “a” of the Index346 previously stored are stored. In other words, in the NextHop-2 (362)to the NextHop-9 (369) of “a-2” to “a-9” of the Index 346, theidentifiers of the NextHop 342 of 2 to 9 previous communications arestored.

It should be noted that the initial values of the NextHop-1 (361) to theNextHop-9 (369) of “a-1” to “a-9” of the Index 346 are set to 0.

[Generation and Updating Examples of a Mesh Path Table]

FIG. 18 is a diagram showing generation and updating examples of themesh path table 350 retained by each of the information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

As shown in a of FIG. 9, the information processing device 100 transmitsthe PREQ by designating the information processing device 240 in theDestSTA field 323 (shown in c of FIG. 4). In this case, when there is nomesh path destined for the information processing device 240, thecontrol unit 140 of the information processing device 100 generates pathinformation of which the destination is set to the destination stationof the PREQ.

Here, when there is a mesh path destined for the information processingdevice 240, the control unit 140 of the information processing device100 extracts the same identifiers as those stored in the current NextHop342 from the identifiers stored in the past NextHop 342 and counts thenumber. In other words, the control unit 140 of the informationprocessing device 100 compares each of the identifiers stored in theNextHop-1 (361) to the NextHop-9 (369) to the identifier stored in theNextHop 342. Then, the control unit 140 of the information processingdevice 100 extracts identifiers which coincide with each other from theidentifiers and counts the number.

Subsequently, the control unit 140 of the information processing device100 sets a value T10 which relates to the expiration time to be storedin the LifeTime 351 according to the number of coinciding identifiers.For example, when the number of coinciding identifiers is 3 or lower,T10=T1 (value stored in the LifeTime field 337 of the PREP) is set. Inaddition, when the number of coinciding identifiers is 4 or higher and 7or lower, T10=T1×2 is set. In addition, when the number of coincidingidentifiers is 8 or higher, T10=T1×3 is set. T10, however, is set to bea value satisfying the following condition.

T10>T2>0

The control unit 140 of the information processing device 100, forexample, stores the sum of the current time (transmission time of thePREQ) and T10 in the LifeTime 351 (“e” of the Index 346) as shown in aof FIG. 18.

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T10 in the ExpTime 345(“d” of the Index 346).

It should be noted that, although the example in which the identifier ofthe NextHop 342 of the 9 previous communications is retained has beenshown in this example, the identifiers of the NextHop 342 of a valueother than the 9 previous communications (8 previous communications orless and 10 previous communications or more) may be retained and used.

In addition, although the example in which T10 is set based on thenumber of coinciding identifiers among those of the NextHop 342 of aplurality of previous communications has been shown in this example, T10may be set based on the number of consecutive identifiers among those ofthe NextHop 342 of the plurality of previous communications.

In this manner, the control unit 140 of the information processingdevice 100 updates the mesh path destined for the information processingdevice 240.

It should be noted that b and c of FIG. 18 are the same as the exampleshown in b and c of FIG. 15 except for the point that the conditions forT3 to T5 are different. In addition, the content of updating the relaystation which has received the PREP (FIG. 16) is the same as the exampleshown in FIG. 16 except for the point that the condition of T4 isdifferent. Thus, description thereof is omitted here.

It should be noted that T3 to T5 are set to have values satisfying thefollowing condition.

T10>T2>T3>T4≧T5>0

As described above, when the same communication path is consecutivelyselected as a mesh path (communication path) updated through exchange ofsignals such as the PREQ and the like, the control unit 140 lengthensthe effective time (expiration time) and updating time (updatingexpiration time). Likewise, when a rate of selection of the same meshpath (communication path) is higher than a predetermined value, thecontrol unit 140 lengthens the effective time (expiration time) andupdating time (updating expiration time).

It should be noted that the control unit 140 of the informationprocessing device 100 may transmit a PREQ by setting the value of theLifeTime field 327 to be T10. In this case, the updating expiration timeand expiration time of a relay station and the destination station ofthe PREQ are decided with reference to T10.

[Example in which the LifeTime is Changed According to a Situation of aLink]

The example in which the LifeTime is changed according to a situation ofa path has been shown above. Here, an example in which the LifeTime ischanged according to a situation of a link will be shown. When asituation of a link is good (for example, the electric field intensityof an information processing device designated as a next hop destinationis higher than a threshold value), for example, the value of theLifeTime can be set to be high (the expiration time can be delayed). Inaddition, when a situation of a link is bad (for example, the electricfield intensity of an information processing device designated as a nexthop destination is equal to or lower than the threshold value), forexample, the value of the LifeTime can be set to be low (the expirationtime can be advanced).

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Thus, the differences will be mainlydescribed, and a part of description regarding common portions to theabove-described example will be omitted.

In addition, since the content of updating is the same as that of FIG.18, it will be described with reference to FIG. 18 in this example.

As shown in a of FIG. 9, the information processing device 100 transmitsthe PREQ by designating the information processing device 240 in theDestSTA field 323 (shown in c of FIG. 4). In this case, when there is nomesh path destined for the information processing device 240, thecontrol unit 140 of the information processing device 100 generates pathinformation of which the destination is set to the destination stationof the PREQ as described above.

Here, when there is a mesh path destined for the information processingdevice 240, the control unit 140 of the information processing device100 sets a value of the LifeTime according to the value of the electricfield intensity of the information processing device of the NextHop 342.Here, the electric field intensity is, for example, a Received SignalStrength Indicator (RSSI).

When the RSSI is lower than −70 dBm, for example, the control unit 140of the information processing device 100 sets T10=T1×0.8. In addition,when the RSSI is −70 dBm or greater and lower than −60 dBm, the controlunit 140 of the information processing device 100 sets T10=T1.Furthermore, when the RSSI is −60 dBm or greater and lower than −40 dBm,the control unit 140 of the information processing device 100 setsT10=T1×2. In addition, when the RSSI is −40 dBm or greater, the controlunit 140 of the information processing device 100 sets T10=T1×3.

In other words, T10 is set as follows.

T10=T1×0.8 if RSSI<−70 dBm

T10=T1 if −70 dBm≦RSSI<−60 dBm

T10=T1×2 if −60 dBm≦RSSI<−40 dBm

T10=T1×3 if −40 dBm≦RSSI

Here, T10 is set to be a value satisfying the following condition.

T10>T2>0

It should be noted that, when there is no mesh path destined for theinformation processing device 240, the control unit 140 of theinformation processing device 100 may set T10=T1.

The control unit 140 of the information processing device 100 stores,for example, the sum of the current time (transmission time of the PREQ)and T10 in the LifeTime 351 (“e” of the Index 346) as shown in a of FIG.18.

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T10 in the ExpTime 345(“d” of the Index 346).

In this manner, the control unit 140 of the information processingdevice 100 generates or updates the mesh path destined for theinformation processing device 240.

It should be noted that generation or updating of a mesh path of a relaystation and the destination station of the PREQ and a relay station ofthe PREP is the same as in the example in which the LifeTime is changedaccording to a situation of a path. Thus, description thereof is omittedhere.

As described above, when the electric field intensity of an informationprocessing device set as a next transmission destination on a mesh path(communication path) is set to be higher than the threshold value, thecontrol unit 140 lengthens the effective time (expiration time) and theupdating time (updating expiration time). On the other hand, when theelectric field intensity of an information processing device set as anext transmission destination is set to be lower than the thresholdvalue, the control unit 140 shortens the effective time (expirationtime) and the updating time (updating expiration time).

[Example in which the LifeTime is Changed According to a Movement Stateof an Information Processing Device]

The examples in which the LifeTime is changed according to situations ofa path and a link have been described above. An example in which theLifeTime is changed according to a movement state of an informationprocessing device will be shown here. In a state in which an informationprocessing device is moving, for example, a value of the LifeTime is setto be small (the expiration time is advanced).

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than the LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Thus, the differences will be mainly describedbelow, and a part of description regarding common portions to theabove-described example will be omitted.

In addition, since the content of updating is the same as in FIG. 18, itwill be described with reference to FIG. 18 in this example.

As shown in a of FIG. 9, the information processing device 100 transmitsthe PREQ by designating the information processing device 240 in theDestSTA field 323 (shown in c of FIG. 4). In this case, when there is nomesh path destined for the information processing device 240, thecontrol unit 140 of the information processing device 100 generates pathinformation of which the destination is set to the destination stationof the PREQ as described above. In addition, when there is a mesh pathdestined for the information processing device 240, the control unit 140of the information processing device 100 updates the path information ofwhich the destination is set to the destination station of the PREQ asdescribed above.

Here, the control unit 140 of the information processing device 100determines whether or not movement of the information processing device100 has been detected. The control unit 140 of the informationprocessing device 100 can detect movement of the information processingdevice 100 based on movement information output from, for example, themovement detection unit 171. In addition, the control unit 140 of theinformation processing device 100 can detect movement of the informationprocessing device 100 based on, for example, a movement distance of theinformation processing device 100 computed by the movement detectionunit 171. It should be noted that the control unit 140 of theinformation processing device 100 may detect movement of the informationprocessing device 100 based on, for example, a change of an electricfield intensity (for example, the RSSI). The control unit 140 of theinformation processing device 100 determines, for example, whether ornot a change of the electric field intensity (a change per unit time)acquired by the information processing device 100 is equal to or greaterthan a predetermined value, and can detect movement of the informationprocessing device 100 based on the determination result.

Then, the control unit 140 of the information processing device 100 setsT10=T1×0.8 when movement of the information processing device 100 hasbeen detected. In addition, when no movement of the informationprocessing device 100 has been detected (i.e., movement of theinformation processing device 100 stops), the control unit 140 of theinformation processing device 100 sets T10=T1. It should be noted thatT10 is set to be a value satisfying the following condition.

T10>T2>0

For example, the control unit 140 of the information processing device100 stores the sum of the current time (transmission time of the PREQ)and T10 in the LifeTime 351 (“e” of the Index 346) as shown in a of FIG.18.

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T10 in the ExpTime 345(“d” of the Index 346).

In this manner, the control unit 140 of the information processingdevice 100 generates or updates the mesh path destined for theinformation processing device 240.

It should be noted that the value of T10 may be set more finelyaccording to a movement speed or a movement distance of the informationprocessing device 100.

It should be noted that generation or updating of a mesh path of a relaystation and the destination station of the PREQ and a relay station ofthe PREP is the same as in the example in which the LifeTime is changedaccording to a situation of a path. Thus, description thereof is omittedhere.

As described above, when the information processing device 100 ismoving, the control unit 140 shortens the effective time (expirationtime) and updating time (updating expiration time).

[Example in which the LifeTime is Changed According to Presence orAbsence of a Path Candidate]

The examples in which the LifeTime is changed according to situations ofa path and a link and a movement state of the information processingdevice have been shown above. Here, an example in which the LifeTime ischanged according to presence or absence of a path candidate of aninformation processing device will be shown. When an informationprocessing device is assumed to serve as a path candidate, for example,a value of the LifeTime is set to decrease (the expiration time isadvanced). Here, the case in which an information processing device isassumed to serve as a path candidate is a case in which, for example,the electric field intensity of another information processing device(an adjacent station) which is not designated as a next hop destinationis higher than a threshold value.

It should be noted that, in this example, a part of the example in whichthe above-described ExpTime is set to be shorter than the LifeTime ismodified, and a part of the mesh path table 350 to be generated (or tobe updated) is different. Thus, the differences will be mainly describedbelow, and a part of description regarding common portions to theabove-described example will be omitted.

In addition, since the content of updating is the same as in FIG. 18, itwill be described with reference to FIG. 18 in this example.

As shown in a of FIG. 9, the information processing device 100 transmitsthe PREQ by designating the information processing device 240 in theDestSTA field 323 (shown in c of FIG. 4). In this case, when there is nomesh path destined for the information processing device 240, thecontrol unit 140 of the information processing device 100 generates pathinformation of which the destination is set to the destination stationof the PREQ as described above. In addition, when there is a mesh pathdestined for the information processing device 240, the control unit 140of the information processing device 100 updates the path information ofwhich the destination is set to the destination station of the PREQ asdescribed above.

Here, the control unit 140 of the information processing device 100determines, for example, whether or not the electric field intensity ofan information processing device (an adjacent station) that is notdesignated in the NextHop 342 is higher than a threshold value. Forexample, the control unit 140 of the information processing device 100determines whether or not the electric field intensity (RSSI) of aninformation processing device whose identifier is not stored in theNextHop 342 is equal to or higher than the threshold value (−60 dBm).Then, when the electric field intensity (RSSI) of the informationprocessing device is less than the threshold value (−60 dBm), T10=T1 isset. In addition, when the electric field intensity (RSSI) of theinformation processing device is equal to or higher than the thresholdvalue (−60 dBm), T10=T1×0.8 is set.

In other words, T10 is set as follows.

T10=T1 if RSSI<−60 dBm

T10=T1×0.8 if −60 dBm≦RSSI

Here, T10 is set to be a value satisfying the following condition.

T10>T2>0

It should be noted that, in this example, the example in which theLifeTime is changed using the electric field intensity of an informationprocessing device (adjacent station) which is not designated in theNextHop 342 is shown; however, the LifeTime may be changed using thedifference between the electric field intensity of the informationprocessing device of the NextHop 342.

For example, the difference between the electric field intensity of aninformation processing device that is not the NextHop 342 (RSSI OTHERS)and the electric field intensity of the information processing device ofthe NextHop (RSSI NEXT) is computed. Then, based on whether or not thedifference is greater than a threshold value (for example, 20 dBm), theLifeTime may be changed. In other words, the LifeTime can be changedbased on whether or not the electric field intensity of an informationprocessing device that is not the NextHop 342 (RSSI OTHERS)−the electricfield intensity of the information processing device of the NextHop 342(RSSI NEXT)>20 dBm is satisfied.

For example, the control unit 140 of the information processing device100 stores the sum of the current time (transmission time of the PREQ)and T10 in the LifeTime 351 (“e” of the Index 346) as shown in a of FIG.18.

In addition, the control unit 140 of the information processing device100 stores the value obtained by subtracting T2 from the sum of thecurrent time (transmission time of the PREQ) and T10 in the ExpTime 345(“d” of the Index 346).

In this manner, the control unit 140 of the information processingdevice 100 generates or updates the mesh path destined for theinformation processing device 240.

It should be noted that the value of T10 may be set more finely.

In addition, generation or updating of a mesh path of a relay stationand the destination station of the PREQ and a relay station of the PREPis the same as in the example in which the LifeTime is changed accordingto a situation of a path. Thus, description thereof is omitted here.

As described above, when the electric field intensity of an informationprocessing device which is not designated as the next transmissiondestination on a mesh path (communication path) is greater than thethreshold value, the control unit 140 shortens the effective time(expiration time) and updating time (updating expiration time).

[Example of a Path Search Start Timing According to a Situation of aLink]

Here, an example in which a path search start timing is set according toa situation of a link will be shown. When a situation of a link is bad,for example, it is controlled to start path search.

For example, the control unit 140 of the information processing device100 monitors packet loss of each adjacent station (each of theinformation processing devices (for example, the information processingdevices 210, 220, and 230 shown in FIG. 1) which is directly linked tothe information processing device 100). Then, the control unit 140 ofthe information processing device 100 determines whether or not there isone with a packet error rate exceeding a threshold value (one with thenumber of packet losses exceeding the threshold value) among theinformation processing devices whose identifiers are stored in theNextHop 342. As a result of the determination, when there is aninformation processing device with a packet error rate exceeding thethreshold value, the control unit 140 of the information processingdevice 100 starts updating of a mesh path of another informationprocessing device passing through the foregoing information processingdevice. In other words, the setting of the path of the other informationprocessing device passing through the foregoing information processingdevice is updated.

In this manner, when there is an information processing device with thenumber of packet losses greater than the threshold value amonginformation processing devices designated as the next transmissiondestinations on a mesh path (communication path), the control unit 140transmits a signal (PREQ) for updating the communication path. Thissignal is transmitted to another information processing device(destination of the mesh path) on the mesh path (communication path)including the foregoing information processing device.

[Example of a Path Search Start Timing when a New Link has beenEstablished]

Here, an example in which a path search start timing is set when a newlink has been established will be shown.

For example, when a new link has been established with an adjacentinformation processing device, the control unit 140 of the informationprocessing device 100 starts updating of a mesh path to the foregoinginformation processing device. In other words, a setting of the path tothe information processing device is started.

In this case, the control unit 140 of the information processing device100 may set, for example, a random delay time before updating of themesh path is started (before a search for the path is started). Then,when the setting of the path is to be started, the control unit 140 ofthe information processing device 100 starts the setting of the pathafter the set random delay time elapses. Accordingly, the informationprocessing devices can be caused not to simultaneously start updating ofthe mesh path.

In this manner, when there is an information processing device of whicha new link has been established with the information processing device100, the control unit 140 transmits a signal for updating the mesh path(communication path) to another information processing device on themesh path (communication path) including the foregoing informationprocessing device. In this case, the control unit 140 transmits thesignal for updating the mesh path (communication path) by setting arandom delay time.

[Example of a Path Search Start Timing when a Link is Disconnected]

Here, an example in which a path search start timing is set when a linkis disconnected will be shown.

For example, when a link with an information processing device whoseidentifier is stored in the NextHop 342 is disconnected, updating of amesh path to another information processing device passing through theforegoing information processing device is started up. In other words, asetting of the path to the other information processing device passingthrough the foregoing information processing device is started.

As described above, when a link with an information processing devicethat is the next transmission destination of a mesh path (communicationpath) is disconnected, the control unit 140 transmits a signal forupdating the mesh path (communication path) to another informationprocessing device on the mesh path (communication path) including theforegoing information processing device.

[Operation Example of an Information Processing Device]

FIGS. 19 to 24 are flowcharts showing an example of the procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology. In FIGS. 19 and 24, asignal processing example corresponding to the example in which theExpTime is changed according to a position on a path (shown in FIGS. 13and 14) is shown.

First, the control unit 140 determines whether or not there is atransmission request for a PREQ (Step S801). When there is atransmission request for a PREQ (Step S801), the control unit 140creates a mesh path table for the destination station of the PREQ (StepS802), and proceeds to Step S805.

When there is no transmission request for a PREQ (Step S801), thecontrol unit 140 determines whether or not there is a mesh path table inwhich an updating expiration time stored in the ExpTime 345 is past thecurrent time (Step S803). When there is a mesh path table in which theupdating expiration time is past the current time (Step S803), thecontrol unit 140 updates the mesh path table for the destination station(Step S804). Subsequently, the control unit 140 creates a PREQ andtransmits the signal to the destination station (Step S805).

When there is no mesh path table in which the updating expiration timeis past the current time (Step S803), the control unit 140 determineswhether or not there is a mesh path table in which the expiration timestored in the LifeTime 351 is past the current time (Step S806). Whenthere is a mesh path table in which the expiration time is past thecurrent time (Step S806), the control unit 140 determines whether or notthe ExpTime 345 of the mesh path table is undefined (Step S807).

Then, when the ExpTime 345 of the mesh path table is undefined (StepS807), the control unit 140 deletes the mesh path table (Step S808) andreturns to Step S801. On the other hand, when the ExpTime 345 of themesh path table is undefined (Step S807), the control unit returns toStep S802.

When there is no mesh path table in which the expiration time is pastthe current time (Step S806), the control unit 140 receives the PREQ anddetermines whether or not the identifier of the DestSTA 323 is of itsown station (Step S809).

When the PREQ is unreceived or the identifier of the DestSTA 323 is notof its own station (Step S809), the control unit 140 receives the PREQand determines whether or not the identifier of the DestSTA 323 is ofanother station (Step S810). It should be noted that another stationrefers to one of the information processing stations other than theinformation processing device 100.

When the PREQ is unreceived or the identifier of the DestSTA 323 is notof another station (Step S810), the control unit 140 receives a PREP anddetermines whether or not the identifier of the OrigSTA 332 is of itsown station (Step S811).

When the PREP is unreceived or the identifier of the DestSTA 323 is notof its own station (Step S811), the control unit 140 receives the PREPand determines whether or not the identifier of the OrigSTA 332 is ofanother station (Step S812).

When the PREP is unreceived or the identifier of the DestSTA 323 is notof another station (Step S812), the control unit 140 does whether or notthere is an instruction to finish the communication process (Step S813).Then, when there is an instruction to finish the communication process(Step S813), the operation of the communication process ends, and whenthere is no instruction to finish the communication process, the controlunit returns to Step S801.

In addition, when the PREQ has been received and the identifier of theDestSTA 323 is of its own station (Step S809), the control unit 140creates a mesh path table for the transmission source station of thereceived PREQ (Step S814).

Subsequently, the control unit 140 determines whether or not theidentifier of the TX STA ADDR 303 of the received PREQ is of thetransmission source station (Step S815), and when the identifier is ofthe transmission source station, the control unit proceeds to Step S817.

When the identifier is not of the transmission source station (StepS815), the control unit 140 creates a mesh path table for thetransmitting station of the received PREQ (Step S816). Subsequently, thecontrol unit 140 creates a PREP in response to the received PREQ,transmits the signal to the transmission source station of the receivedPREQ (Step S817), and returns to Step S801.

In addition, when the PREQ has been received and the identifier of theDestSTA 323 is of another station (Step S810), the control unit 140updates or creates a mesh path table for the transmission source stationof the received PREQ (Step S818).

Subsequently, the control unit 140 determines whether or not theidentifier of the TX STA ADDR 303 of the received PREQ is of thetransmission source station (Step S819), and when the identifier is ofthe transmission source station, the control unit proceeds to Step S821.

When the identifier is not of the transmission source station (StepS819), the control unit 140 creates a mesh path table for thetransmitting station of the received PREQ (Step S820). Subsequently, thecontrol unit 140 creates a mesh path table for the transmission sourcestation of the received PREQ (Step S821). Subsequently, the control unit140 creates a PREQ for transferring the received PREQ, transmits thePREQ in broadcast (Step S822), and returns to Step S801.

In addition, when the PREP has been received and the identifier of theOrigSTA 332 is of its own station (Step S811), the control unit 140updates a mesh path table for the transmission source station of thereceived PREP (Step S823). Then, the control unit returns to Step S801.

In addition, when the PREP has been received and the identifier of theOrigSTA 332 is of another station (Step S812), the control unit 140determines whether or not the result of T3−T5×(HopCount of the PREP+1)is T5 or smaller (Step S824). When the result of T3−T5×(HopCount of thePREP+1) is T5 or smaller (Step S824), the control unit 140 sets T4=T5(Step S825). On the other hand, when the result of T3−T5×(HopCount ofthe PREP+1) exceeds T5 (Step S824), the control unit 140 setsT4=T3−T5×(HopCount of the PREP+1) (Step S826).

Then, the control unit 140 creates a PREP for transferring the receivedPREP and transmits the PREP (Step S827).

Then, the control unit 140 extracts a mesh path for which thetransmission source station of the received PREP is set to the Dest 341from the mesh path table, and sets the NextHop 342 of the mesh path asthe NextHop-2 (Step S828).

Then, the control unit 140 updates the mesh path table for thetransmission source station of the received PREP (Step S829).

Then, the control unit 140 determines whether or not the NextHop-2 isthe transmission source station (OrigSTA) (Step S830), and when theNextHop-2 is the transmission source station (OrigSTA), the control unitproceeds to Step S832. On the other hand, when the NextHop-2 is not thetransmission source station (OrigSTA) (Step S830), the control unit 140updates the mesh path table for the NextHop-2 (Step S831).

Subsequently, the control unit 140 updates the mesh path table for thereceived PREP (Step S832). Subsequently, the control unit 140 determineswhether or not the identifier of the TX STA ADDR 303 of the PREP is ofthe transmission source station (destination station of the PREQ) (StepS833), and when the identifier is of the transmission source station(destination station of the PREQ), the control unit returns to StepS801.

When the identifier is not of the transmission source station(destination station of the PREQ) (Step S833), the control unit 140creates a mesh path table for the transmitting station of the receivedPREP (Step S834), and returns to Step S801.

According to the first embodiment of the present technology describedabove, the updating expiration time (ExpTime) of a mesh path is set tobe sooner than the expiration time (LifeTime) of the mesh path. Inaddition, the updating expiration time (ExpTime) of the mesh path ischanged according to a position of an information processing device onthe mesh path.

In addition, the expiration time (LifeTime) of the mesh path can bechanged according to a state (for example, a movement state, a state ofa link) of an information processing device. Accordingly, when asituation is radically changed, the path can be updated in detail. Onthe other hand, when a situation is not significantly changed,unnecessary updating of a mesh path can be reduced. In other words,generation and management of a communication path of a plurality ofinformation processing devices can be properly performed.

2. Second Embodiment

In the first embodiment of the present technology, the examples in whichthe expiration time and updating expiration time of a mesh path are sethave been shown. In the second embodiment of the present technology, anexample in which a metric value included in a signal such as a PREQ ischanged will be shown. It should be noted that a communication system ofthe second embodiment of the present technology is substantially thesame as the communication system 200 shown in FIG. 1 and the like. Thus,the same reference numerals will be given to portions common to those ofthe communication system 200, and part of description thereof will beomitted.

[Example in which a Metric Value is Changed According to a MovementState of an Information Processing Device]

In this example, an example in which a metric value is changed accordingto a movement state of an information processing device will be shown.In other words, an example in which, in a state in which an informationprocessing device is moving, the device is made difficult to select as apath by changing a metric value will be shown.

FIG. 25 is a flowchart showing an example of the processing procedure ofsignal processing by the information processing device 100 according tothe second embodiment of the present technology.

First, the control unit 140 of the information processing device 100determines whether or not a PREQ has been received (Step S841). Then,when no PREQ has been received (Step S841), the control unit continuesmonitoring.

When a PREQ has been received (Step S841), the control unit 140 of theinformation processing device 100 determines whether or not movement ofthe information processing device 100 has been detected (Step S842). Itshould be noted that a movement detection method can be the same as thatof the first embodiment of the present technology.

When movement of the information processing device 100 has been detected(Step S842), the control unit 140 of the information processing device100 computes a multiplication value by multiplying a predetermined value(for example, 1.5) by the metric value of a link between thetransmitting station of the received PREQ and the self-station (StepS843). Then, the control unit 140 of the information processing device100 computes the path metric value by adding the computed multiplicationvalue to the value stored in the Metric field 326 of the received PREQ(Step S845).

On the other hand, when no movement of the information processing device100 has been detected (Step S842), the control unit 140 of theinformation processing device 100 computes a normal path metric value(Step S844). In other words, the control unit 140 of the informationprocessing device 100 computes the path metric value by adding themetric value of the link between the transmitting station of thereceived PREQ and the self-station to the value stored in the Metricfield 326 of the received PREQ (Step S844).

Subsequently, the control unit 140 of the information processing device100 stores the computed path metric value in the PREQ to be transferred(in the Metric field 326 shown in c of FIG. 4) (Step S845). It should benoted that, since other items of the PREQ to be transferred are the sameas in the first embodiment of the present technology, descriptionthereof is omitted. In addition, the control unit 140 of the informationprocessing device 100 stores the computed path metric value in theMetric 343 (“b” of the Index 346) of the mesh path table 350 (StepS845). It should be noted that, since other items of the mesh path table350 are the same as in the first embodiment of the present technology,description thereof is omitted here.

In this manner, the control unit 140 controls updating of the metricvalue included in the signal such as the PREQ based on a state of theinformation processing device 100. For example, the control unit 140controls the metric value to be great when the information processingdevice 100 is moving.

As described above, in a state in which the information processingdevice 100 is moving, a path metric value is computed by setting themetric value of a link between a transmitting station of the receivedPREQ and the self-station (metric value in path setting control data) tobe greater than the actual value. Accordingly, the informationprocessing device 100 can be difficult to select as a path.

[Example in which a Metric Value is Changed According to a Degree ofTraffic Congestion]

In this example, an example in which a metric value is changed accordingto a degree of traffic congestion will be shown. In other words, anexample in which, in a state of congested traffic, a device is madedifficult to select as a path by changing a metric value will be shown.

FIG. 26 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology. It should be noted thatFIG. 26 is obtained by modifying a part of the procedure shown in FIG.25, and thus the same reference numerals will be given to portionscommon to those of FIG. 25, and part of description thereof will beomitted.

The control unit 140 of the information processing device 100 determineswhether or not an amount of traffic (a value of traffic congestion)exceeds a threshold value (Step S846). Here, the amount of traffic canbe set to, for example, a value obtained for each beacon interval (thesum of the times taken for the self-station to perform transmission andreception). In this case, 50% of the time of the beacon interval can beset as the threshold value. In other words, when the sum of the timestaken for the self-station to perform transmission and reception exceeds50% of the time of the beacon interval, the control unit 140 of theinformation processing device 100 can determine traffic to be congested.

Then, when the amount of traffic exceeds the threshold value (StepS846), the control unit 140 of the information processing device 100computes a multiplication value by multiplying a predetermined value(for example, 1.5) by the metric value of the link between thetransmitting station of the PREQ and the self-station (Step S847). Then,the control unit 140 of the information processing device 100 computes apath metric value by adding the computed multiplication value to thevalue stored in the Metric field 326 of the received PREQ (Step S847).

On the other hand, when the amount of traffic does not exceed thethreshold value (Step S846), the control unit 140 of the informationprocessing device 100 computes the normal path metric value (Step S848).

As described above, when an amount of traffic of the informationprocessing device 100 is greater than the threshold value, the controlunit 140 controls the metric value to be great.

As described above, when an amount of traffic of the informationprocessing device 100 is exceeded, a path metric value is computed bysetting the metric value of a link between the transmitting station ofthe received PREQ and the self-station (metric value in path settingcontrol data) to be greater than the actual value. Accordingly, theinformation processing device 100 can be difficult to select as a path.

[Example in which a Metric Computation Method is Changed According to aTX Data Rate]

In this example, an example in which a metric computation method ischanged according to a TX data rate will be shown. For example, when adata rate is low, influence of an error rate is considerable, but when adata rate is high, there is little influence of an error rate. Thus, inthis example, when a TX data rate is high, influence of an error rate isreduced by not reflecting the error rate.

FIG. 27 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology. It should be noted thatFIG. 27 is obtained by modifying a part of the procedure shown in FIG.25, and thus the same reference numerals will be given to portionscommon to those of FIG. 25, and part of description thereof will beomitted.

The control unit 140 of the information processing device 100 determineswhether or not the TX data rate exceeds a threshold value (Step S850).As this threshold value, for example, 39 (Mbps) can be used.

Here, a metric value ca can be obtained using the following Expression 1in, for example, the IEEE 802.11-2012 standard, as described above.

ca=[O±(Bt/r)]/[1/(1−ef)]  Expression 1

In addition, when a data rate is low, influence of an error rate isconsiderable, but when a data rate is high, there is little influence ofan error rate, as described above. Thus, when the TX data rate exceedsthe threshold value (Step S850), the control unit 140 of the informationprocessing device 100 computes the metric value ca of the link betweenthe transmitting station of the received PREQ and the self-station withthe setting of ef of Expression 1=0 (Step S851). Then, the control unit140 of the information processing device 100 computes a path metricvalue by adding the computed metric value ca to the value stored in theMetric field 326 of the received PREQ (Step S851).

On the other hand, when the TX data rate does not exceed the thresholdvalue (Step S850), the control unit 140 of the information processingdevice 100 computes the normal path metric value ca (i.e., ef ofExpression 1 is not set to 0) (Step S852).

As described above, when an error rate of each link is lower than thethreshold value, the control unit 140 computes a metric value using theerror rate, and when an error rate is higher than the threshold value,the control unit computes a metric value without using the error rate.

As described above, even when an error rate is measured for each linkand a metric value is computed with the measured error rate reflected,if the TX data rate exceeds the threshold value, the error rate is notreflected in the metric value. Accordingly, the influence of the errorrate can be reduced.

[Computation Example of a Metric Value when Information Regarding TXData is not Updated]

In this example, a computation example of a metric value wheninformation regarding TX data is not updated because there is no datatransmission will be shown.

[Configuration Example of a Mesh Path Table]

FIG. 28 is a diagram schematically showing still another example of themesh path table (mesh path table 370) retained by each of theinformation processing devices which constitute the communication system200 according to the second embodiment of the present technology. Itshould be noted that, since a configuration of the mesh path table 370has the same form as in the example shown in a of FIG. 11, illustrationthereof will be omitted here.

Specifically, in FIG. 28, the Index 346, the data name 347, and themeaning 348 are shown as examples of the content of the mesh path table370. The mesh path table 370 shown in FIG. 28 is obtained by adding newinformation to the mesh path table 350 shown in FIG. 11. Specifically,information of reference symbols g and h is newly added information.Thus, in FIG. 28, the same reference symbols are given to portionscommon to those of the mesh path table 350 shown in FIG. 11 and part ofdescription thereof will be omitted. Furthermore, FIG. 28 corresponds tob of FIG. 11.

In the TxTime 371 of “g” of the Index 346, the time at which data isfinally transmitted to an information processing device whose identifieris stored in the NextHop 342 is stored.

In the RSSI TXack 372 of “h” of the Index 346, the electric fieldintensity of acknowledgement of a packet on which data is finallytransmitted to the information processing device whose identifier isstored in the NextHop 342 is stored. In other words, the electric fieldintensity of the beacon right before the final data transmission to theinformation processing device whose identifier is stored in the NextHop342 is stored.

FIG. 29 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology. It should be noted thatFIG. 29 is obtained by modifying a part of the procedure shown in FIG.25, and thus the same reference numerals will be given to portionscommon to those of FIG. 25, and part of description thereof will beomitted.

The control unit 140 of the information processing device 100 computesthe difference between the time stored in the TxTime 371 of “g” of theIndex 346 and the current time, and determines whether or not thedifference exceeds a threshold value (Step S853). This threshold valuecan be set to, for example, 10 (seconds).

When the difference does not exceed the threshold value (Step S853), thecontrol unit 140 of the information processing device 100 determineswhether or not data is yet to be transmitted to the informationprocessing device whose identifier is stored in the NextHop 342 (StepS854).

When data has been transmitted (Step S854), the control unit 140 of theinformation processing device 100 computes the difference between thevalue stored in the RSSI TXack 372 of “h” of the Index 346 and the RSSIof the current beacon (Step S855). Then, the control unit 140 of theinformation processing device 100 determines whether or not the computeddifference exceeds a threshold value (Step S855). This threshold valuecan be set to, for example, 10 (dB).

When the difference between the time stored in the TxTime 371 and thecurrent time exceeds the threshold value (Step S855), the control unit140 of the information processing device 100 estimates the metric valueof the link between the transmitting station of the received PREQ andthe self-station based on the RSSI of the current beacon. Then, thecontrol unit 140 of the information processing device 100 computes thepath metric value by adding the computed metric value to the valuestored in the Metric field 326 of the received PREQ (Step S856).

Here, an estimation method of a metric value will be described. Forexample, the control unit 140 of the information processing device 100retains a correspondence table in which the RSSI of a beacon isassociated with the metric value of the link between the transmittingstation of the PREQ and the self-station. Then, the control unit 140 ofthe information processing device 100 extracts the metric value whichcorresponds to the RSSI of the current beacon from this correspondencetable and sets the extracted metric value as an estimated metric value.It should be noted that the correspondence table may be appropriatelychanged for use according to a connection state.

In addition, also in the case of no transmission (Step S854) or when thedifference between the value stored in the RSSI TXack 372 and the RSSIof the current beacon exceeds the threshold value (Step S855), a metricvalue is estimated in the same manner (Step S856). Further, the pathmetric value is computed (Step S856).

On the other hand, when the difference between the time stored in theTxTime 371 and the current time does not exceed the threshold value(Step S855), the control unit 140 of the information processing device100 computes the normal path metric value (Step S857).

As described above, when an elapsed time from the final datatransmission time to an information processing device designated as thenext transmission destination on a mesh path (communication path) islonger than the threshold value, the control unit 140 estimates a metricvalue based on the current electric field intensity. In addition, alsowhen the difference between the electric field intensity at the time ofthe final data transmission to the information processing device and thecurrent electric field intensity is greater than the threshold value,the control unit 140 estimates a metric value based on the currentelectric field intensity.

As described above, the transmission time of the final data packet to anadjacent station and an electric field intensity are associated andretained, and the difference between the retained transmission time anda current time (non-transmission time) and the difference between theretained electric field intensity and a current electric field intensity(electric field intensity difference) are obtained. Then, when thenon-transmission time exceeds the threshold value, or when the electricfield intensity difference exceeds the threshold value, a metric valueis estimated based on a received electric field intensity and used forcomputing a path metric value.

[Computation Example of a Metric Value] FIG. 30 is diagram schematicallyshowing a computation process of a metric value by the informationprocessing device 100 according to the second embodiment of the presenttechnology. In a and b of FIG. 30, examples in which a conversionprocess 601 in which a received electric field intensity is converted toa TX rate and a TX-rate low-pass filter 602 for metric computation areswitched with each other (604) are shown. It should be noted that theTX-rate low-pass filter 602 for metric computation is a low-pass filterfor averaging TX rates. In addition, an example in which a metric valueis computed (603) based on a TX rate after the switching will be shown.

In a of FIG. 30, an example in which a TX rate at which transmission hassucceeded is directly loaded in the TX-rate low-pass filter 602 isshown.

When transmission has succeeded, for example, a metric value is computedusing a value obtained by averaging TX rates of packets at whichtransmission has succeeded (the output value from the TX-rate low-passfilter 602). On the other hand, when data transmission has stopped for along period of time, a metric value is estimated based on a receivedelectric field intensity (601).

There are cases in which, for example, when a TX rate at whichtransmission has succeeded is obtained after a start of estimation of ametric value based on a received electric field intensity or when areceived electric field intensity considerably fluctuates, the TX rateconsiderably fluctuates.

For example, since the TX-rate low-pass filter 602 is compatible with aconsiderably fluctuating TX rate, a time constant is set to be high.Thus, when an average value actually considerably fluctuates, a responsemay become late.

For example, a case in which data transmission has stopped for a longperiod of time and a metric value is estimated based on a receivedelectric field intensity or a case in which a TX rate at whichtransmission has succeeded is obtained from a state of a receivedelectric field intensity considerably fluctuating is assumed. In thatcase, the value of the TX rate at which transmission has succeeded isset to be directly loaded in the TX-rate low-pass filter 602 toaccelerate convergence on the TX-rate low-pass filter 602. In otherwords, when the TX rate at which transmission has succeeded is obtained,the value of the TX rate at which transmission has succeeded is obtainedis set to be the initial value of the TX-rate low-pass filter 602

In b of FIG. 30, an example in which a TX rate estimated from a receivedelectric field intensity and the average value of the estimated TX rateand an output value of the TX-rate low-pass filter 602 are used for thetime before convergence on the TX-rate low-pass filter 602 is shown.

When a metric value is computed after re-setting in the TX-rate low-passfilter 602, complete convergence on the TX-rate low-pass filter 602 isassumed not to occur immediately even if direct loading of the TX rateis used. Thus, a TX rate estimated from the received electric fieldintensity is used for the time before a given number (for example, 20)of packets are transmitted after switching (604), and thereafter, theoutput value of the TX-rate low-pass filter 602 may be used.

In addition, for the time before the given number of packets aretransmitted after the switching (604), the average value of the TX rateestimated from the received electric field intensity and the TX-ratelow-pass filter 602 (604) may be used.

For example, the TX rate estimated from the received electric fieldintensity is used for the time before the given number (for example, 20)of packets are transmitted after the switching (604). Subsequently, forthe time before a given number (for example, 21 to 40) of packets aretransmitted, the average value of the TX rate estimated from thereceived electric field intensity and the output value of the TX-ratelow-pass filter 602 (605) is used. Subsequently, for the followingpackets (for example, from a 41^(st) packet), the output value of theTX-rate low-pass filter 602 is used.

As described above, when data transmission to an information processingdevice designated as the next transmission destination on a mesh path(communication path) is being performed, the control unit 140 computesthe metric value using the value of the data rate thereof averaged bythe low-pass filter. In addition, when a metric value has been estimatedbased on a current electric field intensity, and a data rate at whichtransmission has succeeded has been acquired, the control unit 140computes the metric value using the data rate as the initial value ofthe low-pass filter. In addition, when the data rate is used as theinitial value of the low-pass filter, the control unit 140 uses a metricvalue estimated based on a current electric field intensity after therate is set to the initial value. Furthermore, the control unit 140 thenuses the average value of the estimated metric value and an output valueof the low-pass filter and then uses the output value of the low-passfilter.

[Example of Recovery to a Path]

Here, an information processing device is assumed to be in link brokenwhen an error rate is measured for each link and the error rate exceedsa threshold value. It is not possible for this information processingdevice to perform transmission after link broken. In addition, when thisstate continues, the error rate is not updated, and the state of linkbroken is kept.

Thus, in the second embodiment of the present technology, when linkbroken is set when an error rate is measured for each link and the errorrate exceeds the threshold value, the error rate is set to be lowered bya predetermined ratio each time a predetermined period of time elapsesfrom the link broken. Here, the predetermined period of time can be, forexample, 5 (seconds), and the predetermined ratio by which the errorrate is lowered can be, for example, 1/2.

As described above, when link broken is set when an error rate of eachlink is greater than the threshold value, the control unit 140 lowersthe error rate each time the predetermined period of time passes afterthe link broken is set.

[Example in which Hysteresis is Applied to Metric Selection]

Next, an example in which hysteresis is applied to metric selection willbe shown.

[Example of Path Selection]

FIG. 31 is a diagram schematically showing path selection of thecommunication system 200 according to the second embodiment of thepresent technology.

The arrow 500 represents a path between the information processingdevice 220 and the information processing device 100 passing through theinformation processing device 210. In addition, the path metric valuecomputed by the information processing device 220 for the pathrepresented by the arrow 500 is set to M1.

In addition, the arrow 501 represents a path between the informationprocessing device 220 and the information processing device 100 passingthrough the information processing device 230. Furthermore, the pathmetric value computed by the information processing device 220 for thepath represented by the arrow 501 is set to M2.

When there are two paths as paths between the information processingdevice 220 and the information processing device 100 as shown in FIG.31, the path metric values M1 and M2 with respect to the two pathsdescribed above are compared and the path of the smaller path metricvalue (superior path) is selected.

However, a case in which two paths are frequently switched when thevalues M1 and M2 that are the path metric values of the two pathsapproximate to each other is assumed. In such a case, it is important toprevent the two paths from being frequently switched. Thus, even whenthe path metric value of a current path is greater than another pathmetric value, if the difference of the values does not exceed athreshold value H1, an original path may remain selected, without a newpath being selected.

For example, in the example shown in FIG. 31, a case in which a path onwhich the NextHop 342 is the information processing device 210 when thedestination station is set to the information processing device 100 (thepath represented by the arrow 500) is selected is assumed. When M1>M2+H1in this case, the information processing device 220 selects the path onwhich the NextHop is the information processing device 230 (the pathrepresented by the arrow 501). On the other hand, when M1≦M2+H1, theinformation processing device 220 keeps the original path (the pathrepresented by the arrow 500) selected.

In addition, the same operation can be applied to a case in which thereare 3 or more path selection candidates. For example, a case in whichthe path metric value of a current path is M1 is assumed. In this case,a path corresponding to the path metric value of which the sum with thethreshold value H1 is lower than M1 is set as a new selection candidate.When there are a plurality of such new selection candidates, a path withthe lowest path metric value among the new selection candidates isselected as the NextHop. This example is shown in FIG. 32.

[Operation Example of an Information Processing Device]

FIG. 32 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology. Here, path metric values ofthree paths will be described as M1 to M3.

First, the control unit 140 of the information processing device 100acquires a new path metric value M1 of a path (first path) correspondingto the current NextHop 342 (Step S861). Further, the control unit 140 ofthe information processing device 100 acquires a new path metric valueM2 of a path (second path) not corresponding to the current NextHop 342(Step S862). Further, the control unit 140 of the information processingdevice 100 acquires a new path metric value M3 of another path (thirdpath) not corresponding to the current NextHop (Step S863).

Subsequently, the control unit 140 of the information processing device100 determines whether or not the path metric value M1 is greater thanthe sum of the path metric value M2 and the threshold value H1 (StepS864). When the path metric value M1 is greater than the sum (M2+H1)(Step S864), the control unit proceeds to Step S866.

In addition, when the path metric value M1 is equal to or smaller thanthe sum (M2+H1) (Step S864), the control unit 140 of the informationprocessing device 100 determines whether or not the path metric value M1is greater than the sum of the path metric value M3 and the thresholdvalue H1 (Step S865). When the path metric value M1 is greater than thesum (M3+H1) (Step S865), the control unit 140 of the informationprocessing device 100 determines whether or not the path metric value M2is smaller than the path metric value M3 (Step S866).

When the path metric value M2 is smaller than the path metric value M3(Step S866), the control unit 140 of the information processing device100 selects the path corresponding to the path metric value M2 as a newNextHop 342 (Step S867). On the other hand, when the path metric valueM2 is equal to or greater than the path metric value M3 (Step S866), thecontrol unit 140 of the information processing device 100 selects thepath corresponding to the path metric value M3 as a new NextHop 342(Step S868).

When the path metric value M1 is less than the sum of the path metricvalue M3 and the threshold value H1 (Step S865), the control unit 140 ofthe information processing device 100 selects the path corresponding tothe current NextHop 342 (path metric value M1) (Step S869).

As described above, there are cases in which there is anothercommunication path having a metric value that is smaller than a metricvalue of a current mesh path (communication path) and of which thedifference from the metric value of the current mesh path (communicationpath) is greater than the threshold value H1. In this case, the controlunit 140 sets the other communication path as a new communication path.In addition, when there are a plurality of other communication paths,the control unit 140 sets a communication path having a smallest metricvalue as a new communication path among the plurality of communicationpaths.

[Example in which Hysteresis is Set to be Small]

The example in which, even when a metric value of a selection candidateis smaller than a metric value of a current path, the selectioncandidate is not selected as a new NextHop is shown above. In otherwords, the example in which, when the metric value of the selectioncandidate is smaller than the metric value of the current path but thesum of the metric value of the selection candidate and the thresholdvalue H1 is not smaller than the metric value of the current path, theselection candidate is not selected as a new NextHop has been shown.

However, if a state of presence of such a selection candidate continuesfor a predetermined period of time (or a predetermined number of times),the selection candidate may be considered to be selected as a newNextHop. Thus, in this example, the example in which, if a state ofpresence of such a selection candidate continues for a predeterminedperiod of time (or a predetermined number of times), the selectioncandidate is selected as a new NextHop will be shown.

[Configuration Example of a Mesh Path Table]

FIG. 33 is a diagram schematically showing still another example of themesh path table (mesh path table 380) retained by each of theinformation processing devices which constitute the communication system200 according to the second embodiment of the present technology. Itshould be noted that, since the configuration of the mesh path table 380has the same form as in the example shown in a of FIG. 11, illustrationthereof will be omitted here.

Specifically, in FIG. 33, the Index 346, the data name 347, and themeaning 348 are shown as examples of the content of the mesh path table380. The mesh path table 380 shown in FIG. 33 is obtained by adding newinformation to the mesh path table 350 shown in FIG. 11. Specifically,information of reference symbols g to i is newly added information.Thus, in FIG. 33, the same reference symbols are given to portionscommon to those of the mesh path table 350 shown in FIG. 11 and part ofdescription thereof will be omitted. Furthermore, FIG. 33 corresponds tob of FIG. 11.

In the NextHopHy 381 of “g” of the Index 346, an identifier of aninformation processing device which is smaller than a path metric valuepassing through an information processing device whose identifier isstored in the NextHop 342 but whose difference does not become thethreshold value H1 is stored. In other words, the identifier of theinformation processing device of which a path metric value is smallerthan the path metric value passing through the information processingdevice whose identifier is stored in the NextHop 342 but the sum of theforegoing path metric value and the threshold value H1 is greater thanthe latter path metric value is stored.

In the HyCount 382 of “h” of the Index 346, the number of times which issmaller than the path metric value passing through the informationprocessing device whose identifier is stored in the NextHop 342 butwhose difference does not become the threshold value H1 is stored. Inother words, the number of times in which the same identifier isconsecutively stored in the NextHopHy 381 is stored.

In the NewNextCount 383 of “i” of the Index 346, the number of times inwhich a different path from that of the previous communication isselected is stored. For example, when a PREQ has been received and adifferent path from that of the previous communication has beenselected, a value of the NewNextCount 383 is incremented for each timeof the selection. The initial value thereof, however, is set to zero.Then, when a PREP is received, the final value of the NewNextCount 383is copied and transmitted.

FIG. 34 is a flowchart showing an example of the procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology. In this example, pathmetric values of two paths are described as M1 and M2.

First, the control unit 140 of the information processing device 100acquires the new path metric value M1 of a path corresponding to thecurrent NextHop 342 (Step S871). In addition, the control unit 140 ofthe information processing device 100 acquires the new path metric valueM2 of a path not corresponding to the current NextHop 342 (Step S872).

Subsequently, the control unit 140 of the information processing device100 determines whether or not the path metric value M1 is greater thanthe sum of the path metric value M2 and the threshold value H1 (StepS873). When the path metric value M1 is greater than the sum (M2+H1)(Step S873), the control unit proceeds to Step S882.

In addition, when the path metric value M1 is equal to or smaller thanthe sum (M2+H1) (Step S873), the control unit 140 of the informationprocessing device 100 determines whether or not the path metric value M1is greater than the path metric value M2 (Step S874).

When the path metric value M2 is equal to or greater than the pathmetric value M1 (Step S874), the control unit 140 of the informationprocessing device 100 stores 0 in the HyCount 382 of “h” of the Index346 (Step S875), and then proceeds to Step S881.

In addition, when the path metric value M1 is greater than the pathmetric value M2 (Step S874), the control unit 140 of the informationprocessing device 100 determines whether or not the value stored in theHyCount 382 of “h” of the Index 346 is 0 (Step S876). When the valuestored in the HyCount 382 is 0 (Step S876), the control unit 140 of theinformation processing device 100 stores 1 in the HyCount 382 (StepS877). In addition, the control unit 140 of the information processingdevice 100 stores “NextID” in the NextHopHy 381 of “g” of the Index 346(Step S877). Then, the control unit proceeds to Step S881. It should benoted that the NextID is an identifier for specifying the path of thepath metric value M2 (identifier of an information processing device(adjacent information processing device) passing on the path of the pathmetric value M2).

In addition, when the value stored in the HyCount 382 is not 0 (StepS876), the control unit 140 of the information processing device 100determines whether or not the “NextID” is stored in the NextHopHy 381 of“g” of the Index 346 (Step S878). When the “NextID” is not stored in theNextHopHy 381 (Step S878), the control unit proceeds to Step S875.

On the other hand, when the “NextID” is stored in the NextHopHy 381(Step S878), the control unit 140 of the information processing device100 determines whether or not the value stored in the HyCount 382 issmaller than a threshold value N1 (Step S879).

When the value stored in the HyCount 382 is smaller than the thresholdvalue N1 (Step S879), the control unit 140 of the information processingdevice 100 adds 1 to the value stored in the HyCount 382 (Step S880).Subsequently, the control unit 140 of the information processing device100 selects the path (path metric value M1) corresponding to the currentNextHop 342 (Step S881).

When the value stored in the HyCount 382 is equal to or greater than thethreshold value N1 (Step S879), the control unit 140 of the informationprocessing device 100 selects the path corresponding to the path metricvalue M2 as a new NextHop (Step S882).

As described above, a case in which another communication path having ametric value smaller than a metric value of a current mesh path(communication path) but whose difference with the metric value of thecurrent mesh path (communication path) is not greater than the thresholdvalue H1 is also assumed. In this case, the control unit 140 setsanother communication path as a new communication path on the conditionthat the state continues for a predetermined period of time or apredetermined number of times (for example, the number of times of thestates is equal to or greater than the threshold value N1).

It should be noted that, although the example in which one path of twois selected as a new NextHop has been shown in this example, this methodcan also be applied to selection from three or more paths. In theselection from three or more paths, information regarding each of thepaths is stored in the NextHopHy 381 and the HyCount 382. In addition,when there are a plurality of paths for which a value stored in theHyCount 382 is equal to or greater than the threshold value N1, forexample, a path with the smallest path metric value can be selected as apath therefrom. Alternatively, for example, a path with the largestvalue stored in the HyCount 382 may be selected as a path.

[Example in which Hysteresis is Set to be Small According to a MovementState of an Information Processing Device]

The example using the fixed threshold values H1 and N1 is shown in FIG.34. When an information processing device is moving in that case, it isalso assumed that a path which is a selection candidate can change atany time.

Thus, when movement of an information processing device has beendetected to correspond to the movement of the information processingdevice, the control unit 140 of the information processing device 100performs a comparison process described above by setting the thresholdvalue H1 to be small. By setting the threshold value H1 to be small asabove when movement of the information processing device has beendetected, it is easy to keep pace with a change of an environment. Itshould be noted that the threshold value N1 may be changed according tothe amount of a change, a speed of a change, or the like.

In addition, when movement of an information processing device has beendetected to correspond to the movement of the information processingdevice, the control unit 140 of the information processing device 100performs a comparison process described above by setting the thresholdvalue N1 to be small. By setting the threshold value N1 to be small asabove when movement of the information processing device has beendetected, it is easy to keep pace with a change of an environment. Itshould be noted that the threshold value N1 may be changed according tothe amount of a change, a speed of a change, or the like.

When the information processing device 100 is moving, the control unit140 sets the metric threshold value (threshold value H1) to be small asdescribed above. Likewise, when the information processing device 100 ismoving, the control unit 140 sets a value relating to a predeterminedperiod of time or a predetermined number of times (threshold value N1)to be small.

[Example in which Hysteresis is Applied with Reflection of Quality ofService (QoS)]

The example in which the threshold values H1 and N1 are changedaccording to a movement state of the information processing device hasbeen shown above. Here, an example in which the threshold values H1 andN1 are changed according to a priority of a packet will be shown. Forexample, since a communication priority order is described in a QoSheader defined in IEEE 80211e or the like, this priority order can beused.

FIG. 35 is a diagram showing four access categories (ACs) of IEEE802.11e-Enhanced Distributed Channel Access (EDCA).

As shown in FIG. 35, in the EDCA, packets are classified into the fouraccess categories (ACs) and stored in each transmission queue. Then, thepackets are transmitted according to each priority. In other words,transmission is sequentially performed from the packet with the highest(1) priority shown in FIG. 35.

Thus, in this example, the threshold value H1 is changed according tothe priority order of the packets. For example, when priority is high,the threshold value H1 is set to be great to cause a path not to beeasily switched. On the other hand, when priority is low, the thresholdvalue H1 is set to be small to easily keep pace with a change of anenvironment. For example, with priority 3 set as a base (i.e., H1×1),the value is 1.5 times (i.e., H1×1.5) in priority 2, 2.0 times (i.e.,H1×2.0) in priority 1, and 0.8 times (i.e., H1×0.8) in priority 4.

In addition, in this example, the threshold value N1 is changedaccording to priority order of packets. For example, when priority ishigh, the threshold value N1 is set to greater to cause a path not to beeasily switched. On the other hand, when priority is low, the thresholdvalue N1 is set to be small to easily keep pace with a change of anenvironment. For example, with priority 3 set as a base (i.e., N1×1),the value is 1.5 times (i.e., N1×1.5) in priority 2, 2.0 times (i.e.,N1×2.0) in priority 1, and 0.8 times (i.e., N1×0.8) in priority 4.

The control unit 140 sets the metric threshold value (threshold valueH1) to be great when priority of communication performed using a meshpath (communication path) is high, and sets the metric threshold value(threshold value H1) to be small when the priority is low, as describedabove. Likewise, the control unit 140 sets a value relating to thepredetermined period of time or the predetermined number of times(threshold value N1) to be great when priority of communicationperformed using a mesh path (communication path) is high, and sets thevalue relating to the predetermined period of time or the predeterminednumber of times (threshold value N1) to be small when the priority islow.

[Example in which Hysteresis is Applied with Reflection of the Number ofHops]

Here, an example in which the threshold values H1 and N1 are changedaccording to the number of hops will be shown. For example, thethreshold values H1 and N1 can be changed using a value stored in theHopCount 352 of the mesh path table 380.

For example, when there are many HopCounts with reference to theHopCount 352 of the mesh path table 380 shown in FIG. 33, the thresholdvalue H1 is set to be great to cause a path not to be easily switched.For example, when a value stored in the HopCount 352 of the mesh pathtable 380 exceeds a threshold value (hop threshold value), the thresholdvalue H1 is set to be great.

On the other hand, when there are few HopCounts with reference to theHopCount 352 of the mesh path table 380, the threshold value H1 is setto be small to easily keep pace with a change of an environment. Forexample, when a value stored in the HopCount 352 of the mesh path table380 is equal to or smaller than the threshold value (hop thresholdvalue), the threshold value H1 is set to be small.

In addition, the threshold value N1 can be changed in the same manner.For example, when there are many HopCounts with reference to theHopCount 352 of the mesh path table 380, the threshold value N1 is setto be great to cause a path not to be easily switched. For example, whena value stored in the HopCount 352 of the mesh path table 380 exceedsthe threshold value (hop threshold value), the threshold value N1 is setto be great.

On the other hand, when there are few HopCounts with reference to theHopCount 352 of the mesh path table 380, the threshold value N1 is setto be small to easily keep pace with a change of an environment. Forexample, when a value stored in the HopCount 352 of the mesh path table380 is equal to or smaller than the threshold value (hop thresholdvalue), the threshold value N1 is set to be small.

When the number of information processing devices on a mesh path(communication path) is greater than the hop threshold value, thecontrol unit 140 sets the metric threshold value (threshold value H1) tobe small as described above. Likewise, when the number of informationprocessing devices on a mesh path (communication path) is greater thanthe hop threshold value, the control unit 140 sets the value relating tothe predetermined period of time or the predetermined number of times(threshold value N1) to be small.

[Example in which Hysteresis is Applied with Reflection of the Number ofTimes of Path Change]

Here, an example in which the threshold values H1 and N1 are changedaccording to the number of times of path change will be shown. Forexample, the threshold values H1 and N1 can be changed using a valuestored in the NewNextCount 383 of the mesh path table 380 shown in FIG.33.

When the value stored in the NewNextCount 383 is great with reference tothe NewNextCount 383, for example, the threshold value H1 is set to begreat to cause a path not to be easily switched. For example, when thevalue stored in the NewNextCount 383 exceeds a threshold value (changethreshold value), the threshold value H1 is set to be great. On theother hand, when the value stored in the NewNextCount 383 is small, thevalue of the threshold value H1 is set to be small to easily keep pacewith a change of an environment. When the value stored in theNewNextCount 383 is equal to or smaller than the threshold value (changethreshold value), the threshold value H1 is set to be small.

In addition, the threshold value N1 can also be changed in the samemanner. For example, when the value stored in the NewNextCount 383 isgreat with reference to the NewNextCount 383, the threshold value N1 isset to be great to cause a path not to be easily switched. For example,when the value stored in the NewNextCount 383 exceeds the thresholdvalue (change threshold value), the threshold value N1 is set to begreat. On the other hand, when the value stored in the NewNextCount 383is small, the value of the threshold value N1 is set to be small toeasily keep pace with a change of an environment. When the value storedin the NewNextCount 383 is equal to or smaller than the threshold value(change threshold value), the threshold value N1 is set to be small.

When the number of changes of mesh paths (communication paths) isgreater than the change threshold value, the control unit 140 sets themetric threshold value (threshold value H1) to be small, as describedabove. Likewise, when the number of changes of mesh paths (communicationpaths) is greater than the change threshold value, the control unit 140sets the value relating to the predetermined period of time or thepredetermined number of times (threshold value N1) to be small.

As described above, according to the second embodiment of the presenttechnology, metric value computation methods are changed according tostates (for example, a movement state, a link state, and the like) ofthe information processing device. Accordingly, the informationprocessing device 100 can be made difficult to select as a path.

In addition, when a mesh path is to be updated, an amount of hysteresisat the time of comparison of mesh paths is controlled according to astate of an information processing device. Accordingly, it is possibleto respond to a case in which switching of a mesh path is stronglyrequired and a situation in which there is no particular desire toswitch a mesh path.

Accordingly, in the embodiments of the present technology, it ispossible to stabilize generation and updating of a mesh path. In otherwords, generation and management of a communication path between aplurality of information processing devices can be properly performed.

In addition, in the embodiments of the present technology, when pathsetting is performed on a multi-hop network, an updating interval and aselection method can be changed according to the number of hops or asituation of an error. Accordingly, unnecessary wireless communicationfor the path setting can be reduced and a stable path can be selected.

3. Application Example

The technology of the present disclosure can be applied to variousproducts. For example, the information processing device 100 may berealized as a mobile terminal such as a smartphone, a tablet-typepersonal computer (PC), a notebook PC, a portable game terminal, or adigital camera, a fixed-type terminal such as a television receiver set,a printer, a digital scanner, or a network storage, or an in-vehicleterminal such as a car navigation device. In addition, the informationprocessing device 100 may be realized as a terminal which performsmachine-to-machine (M2M) communication (which is also referred to as amachine-type communication (MTC) terminal) such as a smart meter, avending machine, a remote monitoring device, or a point-of-sale (POS)terminal. Furthermore, the information processing device 100 may be awireless communication module (for example, an integrated circuit moduleconfigured in one die) mounted in these terminals.

3-1. First Application Example

FIG. 37 is a block diagram showing an example of a schematicconfiguration of a smartphone 900 to which the technology of the presentdisclosure may be applied. The smartphone 900 includes a processor 901,a memory 902, a storage 903, an external connection interface 904, acamera 906, a sensor 907, a microphone 908, an input device 909, adisplay device 910, a speaker 911, a wireless communication interface913, an antenna switch 914, an antenna 915, a bus 917, a battery 918,and an auxiliary controller 919.

The processor 901 may be, for example, a central processing unit (CPU)or a system on a chip (SoC), and controls functions of an applicationlayer and another layer of the smartphone 900. The memory 902 includes arandom access memory (RAM) and a read only memory (ROM), and stores aprogram that is executed by the processor 901, and data. The storage 903may include a storage medium such as a semiconductor memory or a harddisk. The external connection interface 904 is an interface forconnecting an external device such as a memory card or a universalserial bus (USB) device to the smartphone 900.

The camera 906 includes an image sensor such as a charge coupled device(CCD) and a complementary metal oxide semiconductor (CMOS), andgenerates a captured image. The sensor 907 may include a group ofsensors such as a measurement sensor, a gyro sensor, a geomagneticsensor, and an acceleration sensor. The microphone 908 converts soundsthat are input to the smartphone 900 to audio signals. The input device909 includes, for example, a touch sensor configured to detect touchonto a screen of the display device 910, a keypad, a keyboard, a button,or a switch, and receives an operation or an information input from auser. The display device 910 includes a screen such as a liquid crystaldisplay (LCD) and an organic light-emitting diode (OLED) display, anddisplays an output image of the smartphone 900. The speaker 911 convertsaudio signals that are output from the smartphone 900 to sounds.

The wireless communication interface 913 supports one or more ofwireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and11ad to execute wireless communication. The wireless communicationinterface 913 can communicate with another device via a wireless LANaccess point in an infrastructure mode. In addition, the wirelesscommunication interface 913 can directly communicate with another devicein an ad hoc mode. The wireless communication interface 913 cantypically include a baseband processor, a radio frequency (RF) circuit,and a power amplifier. The wireless communication interface 913 may be aone-chip module in which a memory which stores a communication controlprogram, a processor which executes the program and a relevant circuitare integrated. The wireless communication interface 913 may supportother kinds of wireless communication schemes such as a near fieldwireless communication scheme, a proximity wireless communication schemeor a cellular communication scheme in addition to the wireless LANscheme. The antenna switch 914 switches connection destinations of theantenna 915 between a plurality of circuits (for example, circuits fordifferent wireless communication schemes) included in the wirelesscommunication interface 913. The antenna 915 has a single or a pluralityof antenna elements (for example, a plurality of antenna elements whichconstitute a MIMO antenna), which are used by the wireless communicationinterface 913 for transmission and reception of radio signals.

It should be noted that the smartphone 900 is not limited to the exampleof FIG. 36 and may include a plurality of antennas (for example, anantenna for a wireless LAN, an antenna for the proximity wirelesscommunication scheme, etc.). In that case, the antenna switch 914 may beomitted from the configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the wireless communication interface 913, and the auxiliarycontroller 919 to each other. The battery 918 supplies power to blocksof the smartphone 900 illustrated in FIG. 36 via feeder lines, which arepartially shown as dashed lines in the figure. The auxiliary controller919 operates a minimum necessary function of the smartphone 900, forexample, in a sleep mode.

In the smartphone 900 shown in FIG. 36, the communication unit 120, thecontrol unit 140, and the memory 150 described using FIG. 2 may beimplemented by the wireless communication interface 913. In addition, atleast some of these functions may be implemented by the processor 901 orthe auxiliary controller 919.

3-2. Second Application Example

FIG. 37 is a block diagram illustrating an example of a schematicconfiguration of a car navigation device 920 to which the technology ofthe present disclosure may be applied. The car navigation device 920includes a processor 921, a memory 922, a global positioning system(GPS) module 924, a sensor 925, a data interface 926, a content player927, a storage medium interface 928, an input device 929, a displaydevice 930, a speaker 931, a wireless communication interface 933, anantenna switch 934, an antenna 935, and a battery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls anavigation function and another function of the car navigation device920. The memory 922 includes RAM and ROM, and stores a program that isexecuted by the processor 921, and data.

The GPS module 924 uses GPS signals received from a GPS satellite tomeasure a position (such as latitude, longitude, and altitude) of thecar navigation device 920. The sensor 925 may include a group of sensorssuch as a gyro sensor, a geomagnetic sensor, and an air pressure sensor.The data interface 926 is connected to, for example, an in-vehiclenetwork 941 via a terminal that is not shown, and acquires datagenerated by the vehicle, such as vehicle speed data.

The content player 927 reproduces content stored in a storage medium(such as a CD and a DVD) that is inserted into the storage mediuminterface 928. The input device 929 includes, for example, a touchsensor configured to detect touch onto a screen of the display device930, a button, or a switch, and receives an operation or an informationinput from a user. The display device 930 includes a screen such as aLCD or an OLED display, and displays an image of the navigation functionor content that is reproduced. The speaker 931 outputs sounds of thenavigation function or the content that is reproduced.

The wireless communication interface 933 supports one or more ofwireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and11ad to execute wireless communication. The wireless communicationinterface 933 can communicate with another device via a wireless LANaccess point in an infrastructure mode. In addition, the wirelesscommunication interface 933 can directly communicate with another devicein an ad hoc mode. The wireless communication interface 933 cantypically include a baseband processor, an RF circuit, and a poweramplifier. The wireless communication interface 933 may be a one-chipmodule in which a memory which stores a communication control program, aprocessor which executes the program and a relevant circuit areintegrated. The wireless communication interface 933 may support otherkinds of wireless communication schemes such as a near field wirelesscommunication scheme, a proximity wireless communication scheme or acellular communication scheme in addition to the wireless LAN scheme.The antenna switch 934 switches connection destinations of the antenna935 between a plurality of circuits included in the wirelesscommunication interface 933. The antenna 935 has a single or a pluralityof antenna elements, which are used by the wireless communicationinterface 933 for transmission and reception of radio signals.

In addition, the car navigation device 920 may include a plurality ofantennas, not limited to the example of FIG. 37. In that case, theantenna switches 934 may be omitted from the configuration of the carnavigation device 920.

The battery 938 supplies power to blocks of the car navigation device920 illustrated in FIG. 38 via feeder lines that are partially shown asdashed lines in the figure. The battery 938 accumulates power suppliedform the vehicle.

In the car navigation device 920 illustrated in FIG. 37, thecommunication unit 120, the control unit 140, and the memory 150described by using FIG. 2 may be implemented by the wirelesscommunication interface 933. At least a part of the functions may alsobe implemented by the processor 921.

The technology of the present disclosure may also be realized as anin-vehicle system (or a vehicle) 940 including one or more blocks of thecar navigation device 920, the in-vehicle network 941, and a vehiclemodule 942. The vehicle module 942 generates vehicle data such asvehicle speed, engine speed, and trouble information, and outputs thegenerated data to the in-vehicle network 941.

The above-described embodiments are examples for embodying the presenttechnology, and matters in the embodiments each have a correspondingrelationship with disclosure-specific matters in the claims. Likewise,the matters in the embodiments and the disclosure-specific matters inthe claims denoted by the same names have a corresponding relationshipwith each other. However, the present technology is not limited to theembodiments, and various modifications of the embodiments may beembodied in the scope of the present technology without departing fromthe spirit of the present technology.

The processing sequences that are described in the embodiments describedabove may be handled as a method having a series of sequences or may behandled as a program for causing a computer to execute the series ofsequences and recording medium storing the program. As the recordingmedium, a hard disk, a CD (Compact Disc), an MD (MiniDisc), and a DVD(Digital Versatile Disc), a memory card, and a Blu-ray disc (registeredtrademark) can be used.

Effects described in the present description are just examples, theeffects are not limited, and there may be other effects.

Additionally, the present technology may also be configured as below.

(1)

An information processing device including:

a communication unit configured to perform exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and

a control unit configured to perform control to change a metric valueincluded in the signal based on a state of the information processingdevice.

(2)

The information processing device according to (1), wherein, when theinformation processing device is moving, the control unit sets themetric value to be large.

(3)

The information processing device according to (1) or (2), wherein, whenan amount of traffic of the information processing device is larger thana threshold value, the control unit sets the metric value to be large.

(4)

The information processing device according to any of (1) to (3),wherein, when an error rate of each link is lower than a thresholdvalue, the control unit computes the metric value using the error rate,and when the error rate is higher than the threshold value, the controlunit computes the metric value without using the error rate.

(5)

The information processing device according to any of (1) to (4),wherein, when a time elapsed from a final data transmission time to aninformation processing device which is designated as a next transmissiondestination on the communication path is longer than a threshold value,or when a difference between an electric field intensity at the time ofthe final data transmission to the information processing device and acurrent electric field intensity is larger than a threshold value, thecontrol unit estimates the metric value based on the current electricfield intensity.

(6)

The information processing device according to (5), wherein, when datatransmission to the information processing device which is designated asthe next transmission destination on the communication path isperformed, the control unit computes the metric value using a valueobtained by averaging a rate of the data using a low-pass filter, andwhen the metric value is estimated based on the current electric fieldintensity and a rate of the data at which transmission has succeeded hasbeen acquired, the control unit computes the metric value using the rateof the data as an initial value of the low-pass filter.

(7)

The information processing device according to (6), wherein, when therate of the data is used as the initial value of the low-pass filter,the control unit uses a metric value estimated based on the currentelectric field intensity after the setting of the initial value, thenuses an average value of the estimated metric value and an output valueof the low-pass filter, and then uses the output value of the low-passfilter.

(8)

The information processing device according to any of (1) to (7),wherein, when link broken is set if an error rate of each link is higherthan a threshold value, the control unit lowers the error rate each timea predetermined period of time elapses from the link broken.

(9)

The information processing device according to any of (1) to (8),wherein, when there is a communication path set based on a magnitude ofthe metric value, and there is another communication path having ametric value which is a metric value smaller than the metric valuerelating to the communication path and whose difference with the metricvalue relating to the communication path is higher than a metricthreshold value, the control unit sets the other communication path as anew communication path.

(10)

The information processing device according to (9), wherein, when thereare a plurality of other communication paths, the control unit sets acommunication path having a smallest metric value among the plurality ofcommunication paths as the new communication path.

(11)

The information processing device according to (9), wherein, when thereis the communication path set based on the magnitude of the metricvalue, and there is another communication path having a metric valuewhich is a metric value smaller than the metric value relating to thecommunication path and whose difference with the metric value relatingto the communication path is not higher than a metric threshold value,the control unit sets the other communication path as the newcommunication path on a condition that this state continues for apredetermined period of time or a predetermined number of times.

(12)

The information processing device according to (9), wherein, when theinformation processing device is moving, the control unit sets themetric threshold value to be small.

(13)

The information processing device according to (11), wherein, when theinformation processing device is moving, the control unit sets a valuerelating to the predetermined period of time or the predetermined numberof times to be small.

(14)

The information processing device according to (9), wherein, whenpriority of communication performed using the communication path ishigh, the control unit sets the metric threshold value to be large, andwhen the priority is low, the control unit sets the metric thresholdvalue to be small.

(15)

The information processing device according to (11), wherein, whenpriority of communication performed using the communication path ishigh, the control unit sets a value relating to the predetermined periodof time or the predetermined number of times to be large, and when thepriority is low, the control unit sets the value relating to thepredetermined period of time or the predetermined number of times to besmall.

(16)

The information processing device according to (9), wherein, when thenumber of information processing devices on the communication path islarger than a hop threshold value, the control unit sets the metricthreshold value to be small.

(17)

The information processing device according to (11), wherein, when thenumber of information processing devices on the communication path islarger than a hop threshold value, the control unit sets a valuerelating to the predetermined period of time or the predetermined numberof times to be small.

(18)

The information processing device according to (9), wherein, when thenumber of times the communication path is changed is larger than athreshold value of the change, the control unit sets the metricthreshold value to be small.

(19)

The information processing device according to (11), wherein, when thenumber of times the communication path is changed is larger than athreshold value of the change, the control unit sets the value relatingto the predetermined period of time or the predetermined number of timesto be small.

(20)

An information processing method including:

a communication procedure of performing exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and

a control procedure of performing control to change a metric valueincluded in the signal based on a state of the information processingdevice.

REFERENCE SIGNS LIST

-   100, 210, 220, 230, 240 information processing device-   110 antenna-   120 communication unit-   130 I/O interface-   140 control unit-   150 memory-   160 bus-   171 movement detection unit-   172 operation reception unit-   173 display unit-   174 audio output unit-   200 communication system-   900 smartphone-   901 processor-   902 memory-   903 storage-   904 external connection interface-   906 camera-   907 sensor-   908 microphone-   909 input device-   910 display device-   911 speaker-   913 wireless communication interface-   914 antenna switch-   915 antenna-   917 bus-   918 battery-   919 auxiliary controller-   920 car navigation device-   921 processor-   922 memory-   924 GPS module-   925 sensor-   926 data interface-   927 content player-   928 storage medium interface-   929 input device-   930 display device-   931 speaker-   933 wireless communication interface-   934 antenna switch-   935 antenna-   938 battery-   941 in-vehicle network-   942 vehicle module

1. An information processing device comprising: a communication unitconfigured to perform exchange of a signal for generation or updating ofa multi-hop communication path using wireless communication with anotherinformation processing device; and a control unit configured to performcontrol to change a metric value included in the signal based on a stateof the information processing device.
 2. The information processingdevice according to claim 1, wherein, when the information processingdevice is moving, the control unit sets the metric value to be large. 3.The information processing device according to claim 1, wherein, when anamount of traffic of the information processing device is larger than athreshold value, the control unit sets the metric value to be large. 4.The information processing device according to claim 1, wherein, when anerror rate of each link is lower than a threshold value, the controlunit computes the metric value using the error rate, and when the errorrate is higher than the threshold value, the control unit computes themetric value without using the error rate.
 5. The information processingdevice according to claim 1, wherein, when a time elapsed from a finaldata transmission time to an information processing device which isdesignated as a next transmission destination on the communication pathis longer than a threshold value, or when a difference between anelectric field intensity at the time of the final data transmission tothe information processing device and a current electric field intensityis larger than a threshold value, the control unit estimates the metricvalue based on the current electric field intensity.
 6. The informationprocessing device according to claim 5, wherein, when data transmissionto the information processing device which is designated as the nexttransmission destination on the communication path is performed, thecontrol unit computes the metric value using a value obtained byaveraging a rate of the data using a low-pass filter, and when themetric value is estimated based on the current electric field intensityand a rate of the data at which transmission has succeeded has beenacquired, the control unit computes the metric value using the rate ofthe data as an initial value of the low-pass filter.
 7. The informationprocessing device according to claim 6, wherein, when the rate of thedata is used as the initial value of the low-pass filter, the controlunit uses a metric value estimated based on the current electric fieldintensity after the setting of the initial value, then uses an averagevalue of the estimated metric value and an output value of the low-passfilter, and then uses the output value of the low-pass filter.
 8. Theinformation processing device according to claim 1, wherein, when linkbroken is set if an error rate of each link is higher than a thresholdvalue, the control unit lowers the error rate each time a predeterminedperiod of time elapses from the link broken.
 9. The informationprocessing device according to claim 1, wherein, when there is acommunication path set based on a magnitude of the metric value, andthere is another communication path having a metric value which is ametric value smaller than the metric value relating to the communicationpath and whose difference with the metric value relating to thecommunication path is higher than a metric threshold value, the controlunit sets the other communication path as a new communication path. 10.The information processing device according to claim 9, wherein, whenthere are a plurality of other communication paths, the control unitsets a communication path having a smallest metric value among theplurality of communication paths as the new communication path.
 11. Theinformation processing device according to claim 9, wherein, when thereis the communication path set based on the magnitude of the metricvalue, and there is another communication path having a metric valuewhich is a metric value smaller than the metric value relating to thecommunication path and whose difference with the metric value relatingto the communication path is not higher than a metric threshold value,the control unit sets the other communication path as the newcommunication path on a condition that this state continues for apredetermined period of time or a predetermined number of times.
 12. Theinformation processing device according to claim 9, wherein, when theinformation processing device is moving, the control unit sets themetric threshold value to be small.
 13. The information processingdevice according to claim 11, wherein, when the information processingdevice is moving, the control unit sets a value relating to thepredetermined period of time or the predetermined number of times to besmall.
 14. The information processing device according to claim 9,wherein, when priority of communication performed using thecommunication path is high, the control unit sets the metric thresholdvalue to be large, and when the priority is low, the control unit setsthe metric threshold value to be small.
 15. The information processingdevice according to claim 11, wherein, when priority of communicationperformed using the communication path is high, the control unit sets avalue relating to the predetermined period of time or the predeterminednumber of times to be large, and when the priority is low, the controlunit sets the value relating to the predetermined period of time or thepredetermined number of times to be small.
 16. The informationprocessing device according to claim 9, wherein, when the number ofinformation processing devices on the communication path is larger thana hop threshold value, the control unit sets the metric threshold valueto be small.
 17. The information processing device according to claim11, wherein, when the number of information processing devices on thecommunication path is larger than a hop threshold value, the controlunit sets a value relating to the predetermined period of time or thepredetermined number of times to be small.
 18. The informationprocessing device according to claim 9, wherein, when the number oftimes the communication path is changed is larger than a threshold valueof the change, the control unit sets the metric threshold value to besmall.
 19. The information processing device according to claim 11,wherein, when the number of times the communication path is changed islarger than a threshold value of the change, the control unit sets thevalue relating to the predetermined period of time or the predeterminednumber of times to be small.
 20. An information processing methodcomprising: a communication procedure of performing exchange of a signalfor generation or updating of a multi-hop communication path usingwireless communication with another information processing device; and acontrol procedure of performing control to change a metric valueincluded in the signal based on a state of the information processingdevice.